2001 – Marrakech


Ninth Annual Meeting of ISBN

Date: May 6 – May10, 2001
Place: Marrakech, Morocco
Venue: Palmeraie Golf Palace & Resort


 SYMPOSIA

2001: A Frontal-lobe Odyssey; Organized by Adrian Owen and Brad Postle
Participants: Randy Buckner, Washington University; John Duncan, MRC Cognition and Brain Sciences Unit; Apostolos Georgopoulos, University of Minnesota; Earl Miller, MIT; Yuko Munakata, University of Colorado; Randy O’Reilly, University of Colorado; Michael Petrides, McGill University

Probing the Infant Mind; Organized by Julie Fiez
Participants: Susan Johnson, Stanford University; Seth Pollak, University of Wisconsin-Madison; Fei Xu, Northeastern University; Julie Fiez, University of Pittsburgh; Jenny Saffran, University of Wisconsin-Madison.

The Cingulate Cortices; Organized by John Aggleton
Participants: John Aggleton, Cardiff University; Tomas Paus, McGill University; Timothy J. Bussey, Cambridge University; Matthew Rushworth, Oxford University.


PROGRAM

Sunday

6th Afternoon Session

4:15 Welcome and Orienting Notes

Works in Progress

4:30 Hormonal and Age-related Factors Affecting Prefrontal Neuroanatomy and Related Cognition in

Healthy Women

P.E. Cowell1, I.D. Wilkinson2, J.A.Webb3, C.A.J. Romanowski2, S. Keller3, H.F. Richards1, and N. Roberts3

1.Dept. Human Communication Sciences, University of Sheffield, Sheffield, UK 2.Academic Radiology, University of Sheffield, Sheffield, UK. 3. MARIARC, University of Liverpool, Liverpool, UK.

Previous studies have shown that the aging process differentially affects the neurocognitive profiles of men and women. However, results across studies haven’t always been consistent. Failure to match for sources of within-sex variation may partially explain this lack of replication. The current work-in-progress examines effects of menopause and hormone replacement therapy (HRT) on regional neuroanatomy of the prefrontal cortex (PFC) and related cognitive measures in 24 healthy women (aged 20-67). Participants were part of a larger study including 21 men (aged 22-72) that showed significant interactions of sex and age with regional PFC volumes derived from MRI. In the current analysis, female participants were grouped according to menopausal status and HRT history to examine how these factors contributed to differences among women, particularly those aged 50-67. Premenopausal women and postmenopausal women with history of HRT tended to perform better than perimenopausal and postmenopausal women without history of HRT on cognitive measures associated with prefrontal function, including Corsi blocks, digit span and Wisconsin Card Sort Test. A similar trend was seen for the right medial orbital PFC, with premenopausal women and postmenopausal women with history of HRT having larger volumes. These preliminary findings will be discussed in relation to individual differences in neurocognitive aging.

4:50 Studies of Visual and Auditory Temporal Processing in Children Born Small-for-Gestational-Age: Do Deficits in these Areas Contribute to Reading Problems?

Lorna S. Jakobson1, Andrea L.S. Downie2, Virginia Frisk2 and Irene Ushycky2

1Department of Psychology, University of Manitoba (Winnipeg, Manitoba, Canada) and 2The Hospital for Sick Children (Toronto, Ontario, Canada).

The results of numerous studies suggest that children born small-for-gestational-age (SGA) are at risk for deficits in academic, cognitive, and intellectual functioning, and for problems with both language and visuomotor development. Investigations presently underway in our laboratory are designed to test the hypothesis that difficulties in some of these areas may reflect the presence of an underlying, general problem with the processing of “temporal” information. We have found that children born SGA do worse than full-term controls born at an appropriate size for their gestational age on tests requiring visual motion processing (a motion-defined form recognition test) and on those requiring auditory temporal order judgements. In addition, preliminary analyses indicate that, within the population of SGA children, the presence of auditory temporal processing problems is associated with deficits in reading, even when the degree of growth restriction, gestational age, Full Scale IQ and auditory working memory have been accounted for.

5:10 Neuropsychological Evaluation of MELAS Syndrome: A Case Study

Sandy A. Neargarder and Michael P. Murtagh

Department of Psychology, Bridgewater State College, Bridgewater, MA 02325 and Boston University, Department of Psychology, Boston, MA 02215

MELAS (myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) is part of a group of diseases known as mitochondrial encephalopathies that were first described in 1984. MELAS is associated with a variety of physical impairments including short stature, seizures, hearing and vision loss, strokes, dementia, ragged red muscle fibers, headaches, loss of voluntary motor control ,cardiomyopathy, and cortical atrophy. Individuals with MELAS develop normally in early childhood and do not manifest symptoms of the disease until between the ages of 6 and 40 years of age. This disorder is progressive in nature with a mean age of death reported at 33 years.

Although the physical symptoms accompanying this disorder are fairly well-defined, the neuropsychological functioning of MELAS patients has yet to be investigated. The current project attempts to examine this issue by

administering a detailed neuropsychological battery to a 13-year-old patient with MELAS syndrome. This battery covers various aspects of neuropsycholgical functioning including general IQ, verbal and nonverbal memory skills, attention and executive functioning, visuospatial abilities, verbal abilities, and basic vision skills. Information derived from these assessments will 1) aid in identifying specific behavioral deficits associated with this disorder, 2) enable speculations regarding brain area involvement, and 3) promote the development of learning intervention strategies for individuals possessing this disorder.

5:30 Performance of Colored-Hearing Synesthetes on Stroop-type and Visual Search Tasks

J.A. Howard and A. Cronin-Golomb

Department of Psychology, Boston University, Boston MA

Colored-hearing synesthesia is a condition in which the experience of color is evoked in response to sounds. These colors do not change over time, and are elicited automatically whenever the appropriate stimulus is perceived. Synesthetic experiences cannot be suppressed, even when they interfere with the performance of behavioral tasks. In this study, Stroop-type and visual search tasks were presented to four colored-hearing synesthetes, all of whom reported that letters of the alphabet elicited colors, and to three non-synesthetic control participants. On the Stroop-type task, it was expected that synesthetes would require a longer amount of time to name the colors of list items that were incongruent with their experiences, as compared to when items were congruent, an effect that would not occur among the control subjects. On the visual search task, it was expected that synesthetes would locate target items faster when they were congruent with their experiences as compared to when they were incongruent. Again, control subjects were not expected to demonstrate any differences across different target conditions. The hypotheses were supported for some participants but not others. Possible explanations for the obtained results include individual differences related to the experience of synesthesia, inaccurate color palettes, and inconsistencies in task difficulty. (Supported by a Sigma Xi Grant in Aid of Research.)

Traditional Paper Session

5:50 Event-related fMRI Discriminates the Discrimination of the Recognition of Familiar and Unfamiliar Objects

Janine Mendola

Center for Advanced Imaging, West Virginia University, Morgantown, WV, USA

Presenting fragmented line drawings in an ascending order of completeness may be used as a tool for studying the cortical localization and dynamics of object recognition. Previous ERP studies have marked the transition from no-identification to identification of such line drawings (Viggiano et al., 1996). We report here an fMRI study aimed at localizing the foci of these signals. In addition, we demonstrate that primed objects can result in either greater or lesser activity than novel objects depending on the location within the cortical network. Finally, a meta-analysis of the results of several recent studies using similar paradigms will be discussed.

6:10 Retention of the Mnemonic Representation of Faces across the ABBA Task in PFC and FFA

Bradley R. Postle1, Jason Druzgal2, and Mark D’Esposito3

1Dept. of Psychology, Univ. of Wisconsin, 2Inst. of Neurological Sciences, Univ. of Pennsylvania, 3Helen Wills Neuroscience Inst. and Dept. of Psychology, Univ. of California, Berkeley, USA

The human lesion literature indicates that performance of simple span and delayed-response tests can be independent of prefrontal cortical (PFC) integrity . This same literature, together with electrophysiological studies in monkeys, also suggests that PFC may play an important role in maintenance of information across distracted delays. We used event-related fMRI to trace the retention of mnemonic representation of target faces across the multiple delays and interposed distracting stimuli that occur in the “ABBA” delayed-recognition task . The task featured three 7 sec. delay periods that were interposed between the presentation of the first and second, second and third, and third and forth stimuli (D1, D2, and D3, respectively). We first identified D1-specific activity in PFC/insula, fusiform face area (FFA), and posterior parietal cortex (PPC). In each subject, only a subset of these PFC/insula and FFA voxels retained the signal during D2. And in each subject, only a smaller subset of these FFA voxels retained the signal during D3. An ROI-based group analysis confirmed that only FFA demonstrated reliable retention of target-specific activity across all delay periods. Our results suggest that PFC does not store mnemonic representations across distracted delay periods. Its role may be to control the maintenance of mnemonic representations that are supported in posterior cortex.


Monday

7th All Day Symposium

A Frontal Lobe Odyssey

Adrian Owen and Brad Postle

9:00 Michael Petrides

Montreal Neurological Institute, McGill University, 3801 University St, Montreal Que, CANADA

tba

10:00 Parallel Processing Of Serial Movements In Prefrontal Cortex

Averbeck BB, Chafee MV, Crowe DA, Georgopoulos AP

Brain Sciences Center, Veterans Affairs Medical Center, Minneapolis MN 55417, USA

A key idea in Lashley’s formulation of the problem of serial order in behavior is the postulated neural representation of all serial elements before the action begins. We investigated this question by recording simultaneously the activity of small neuronal ensembles in prefrontal cortex while monkeys copied geometrical shapes shown on a screen. The shapes were drawn as sequences of movement segments which were associated with distinct patterns of neuronal ensemble activity. We found that these patterns were present during the time preceding the execution of the sequence. In addition, the rank of the strength of representation of a segment in the neuronal population during that time predicted the serial position of the segment in the motor sequence such that, for example, the segment with the highest strength was the first in the sequence, the one with the second highest strength was the second in the sequence, etc. These findings confirm Lashley‚s hypothesis above and provide a neural code for the serial order of segments in a sequence. (Supported by USPHS grant NS17413.)

BREAK

11:30 Interactions Between Frontal Cortex and Basal Ganglia in Working Memory: A Computational Model

Randall C. O’Reilly, Michael J. Frank, & Bryan Loughry

Department of Psychology, University of Colorado, Boulder, Colorado, USA

The frontal cortex and basal ganglia interact via a relatively well-understood and elaborate system of interconnections. In the context of motor function, these interconnections can be understood as disinhibiting or “releasing the brakes” on frontal motor action plans — the basal ganglia detect appropriate contexts for performing motor actions, and enable the frontal cortex to execute such actions at the appropriate time. We build on this idea in the domain of working memory through the use of computational neural network models of this circuit. In our model, the frontal cortex exhibits robust active maintenance, while the basal ganglia contribute a selective, dynamic gating function that enables frontal memory representations to be rapidly updated in a task-relevant manner. We apply the model to a novel version of the continuous performance task (CPT) that requires subroutine-like selective working memory updating, and compare and contrast our model with other existing models and theories of frontal cortex–basal ganglia interactions.

LUNCH

1:30 Prefrontal Cortex and the Neural Basis of Cognitive Control

Earl K. Miller

Center for Learning and Memory, RIKEN-MIT Neuroscience Research Center, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 USA

Our research interests center around the neural mechanisms of attention, learning and memory needed for voluntary, goal-directed, behavior. Much effort is directed at the prefrontal cortex, a brain region associated with the highest levels of cognition. We explore prefrontal function largely by combining a sophisticated behavioral methodology with techniques for examining the activity of ensembles of neurons. The prefrontal cortex (PFC), a cortical region at the anterior end of the brain, has long been known play a central role in orchestrating complex thoughts and actions. Its damage or dysfunction disrupts our ability to ignore distractions, hold important information “in mind”, plan behavior, and control impulses. Results from our laboratory have shown that PFC neurons have complex properties that are ideal for a region thought to be the brain’s “executive”. They are involved in directing attention, in recalling stored memories, and they piece together the diverse information needed for a common behavioral goal. Perhaps most importantly, they transmit acquired knowledge. Their activity reflects the learned associations between cues, actions, and consequences that describe the contingencies of a given task. In short, they seem to underlie our internal representations of the “rules of the game”. This may provide the necessary foundation for the complex behavior of primates, in whom this structure is most elaborate.

2:30 An Adaptive Coding Model of Prefrontal Function

John Duncan

MRC Cognition and Brain Sciences Unit, 15 Chaucer Rd, Cambridge CB2 2EF, UK

Data from human neuroimaging and monkey electrophysiology are used to motivate a new model of prefrontal function, the adaptive coding model. Imaging data show that much the same frontal regions – the cortex surrounding the inferior frontal sulcus, the frontal operculum/anterior insula, and the dorsal anterior cingulate – are activated by increasing demands in a wide variety of cognitive domains, including perception, response selection, working memory, problem solving and executive control. Monkey single cell data show the adaptability of lateral frontal neurons, with conspicuous tuning by current task demands: Whatever the task a monkey has been trained to carry out, task-relevant responses of many different kinds are found intermingled throughout the lateral frontal cortex. New data are presented to show strong attentional selectivity in frontal neurons, with effective filtering out of stimulus distinctions immaterial to a current task. According to the adaptive coding model, neurons in selected frontal regions adapt their properties to code just that information of relevance to current behaviour. In turn, this selectivity gives support to coding of related information in posterior brain systems, in this way acting as a global attentional controller. The model casts light on a number of related problems, including broad cognitive disorganization following frontal lobe damage, and the phenomenon of “general intelligence” in normal cognition.

BREAK

4:00 Yuko Munakata,

University of Colorado;

tba

5:00 Functional Brain Imaging of Memory Encoding in Young and Older Adults

Randy L. Buckner

Howard Hughes Medical Institute at Washington University, USA

tba


Tuesday

Morning Session: _ Day Symposium

Probing the Infant and Child Mind

Julie Fiez

9:00 Can Developmental Studies of Literacy Teach Us about Reading in Adults?

Julie Fiez

Department of Pychology, University of Pittsburgh

There have been over 10 neuroimaging studies of skilled adult reading. The results converge to identify a network of brain regions that are active during single word reading. However, there is less consensus about the specific contributions of regions within this larger network. In this talk, I will review the findings in adult readers, and then discuss how behavioral and neuroimaging studies in normal and dyslexic children can provide novel information about the brain regions and cognitive processes that contribute to reading.

9:30 Statistical Learning by Human Infants

Jenny Saffran

Department of Psychology, University of Wisconsin — Madison

In this talk I will present results from several experiments suggesting that infant learners possess the ability to detect and use statistical properties of linguistic input in the service of language acquisition. This learning process is basic, implicit, and of potential use for learning in multiple domains. Considerations regarding plasticity and modularity will be discussed.

10: 00 Number Representations in Infants

Fei Xu

Department of Psychology, Northeastern University

Recent studies have found that pre-linguistic infants have two systems for representing number: a “small number” system and a large number system. The former can keep track of up to 3 or 4 individual objects simultaneously and it is the same as the object-tracking system proposed in the object-based attention literature in adults; the latter is a system for estimating large numerosities and it is the same as was found in non-human animals such as rats and pigeons. We suggest that verbal counting may allow us to represent exact numbers that are larger than 3. Some neuroimaging data with adults provide preliminary evidence for this speculation.

BREAK

11:00 Children’s Perception of Emotion in Faces: Domain-general or Domain-specific Learning Mechanisms?

Seth Pollack

Departments of Psychology, Psychiatry, and Pediatrics and Waisman Research Center,

University of Wisconsin at Madison

Emotional signals, such as facial expressions, have long been regarded as important environmental cues that require immediate and accurate recognition (Darwin, 1872). In fact, young children are very skilled at understanding facial expressions of emotion, and demonstrate a high level of expertise reading facial signals at an early age. Yet little is known about the developmental processes involved in the rapid perception and categorization of emotional cues. This talk will examine the extent to which the development of affective perceptual categories are constrained by (a) general properties of affective input, (b) maturational constraints of the developing child, (c) and tuning through social experience.

11: 30 Developmental Approaches to Social Cognition

Susan Johnson

Department of Psychology, Stanford University

Recent work with non-human primates and human adults has yielded interesting preliminary hypotheses about the neural substrates underlying social cognition. This talk will address the relationship between those hypotheses and related developmental work in human infants and people with autism, particularly with respect to theory of mind. Directions for future work will be emphasized.

Tuesday Afternoon (Traditional Paper Session)

1:30 Language and the Autistic Brain: Insights from Neuroimaging

Mirella Dapretto (potential new member)

Dept. of Psychiatry and Biobehavioral Sciences,UCLA School of Medicine, Ahmanson-Lovelace Brain Mapping Center,660 Charles E. Young Drive South,Los Angeles, CA 90095 USA

Linguistic impairments in the realm of social communication are hallmark features of autism. Even in high-functioning autistic individuals, good mastery of the formal aspects of language (e.g., phonology, syntax) is often associated with deficits at the pragmatic and discourse level (e.g., understanding the communicative intentions of others, understanding and using prosodic cues appropriately). Despite considerable evidence of both structural and functional abnormalities in the autistic brain, we still know very little about the neural underpinnings of these communicative impairments. Indeed, while recent neuroimaging data have allowed for significant strides to be made in our understanding of the neural representation of language, the neural correlates of these linguistic and communicative functions are still poorly characterized even in the normal brain (adult or still developing). In the present talk, I will describe our approach to begin to delineate the brain circuitry subserving the high-level linguistic functions that are often impaired in autism in order to address competing hypotheses about the underlying nature of these impairments. In doing so, I will present functional magnetic resonance imaging data gathered on normal adults, as well as on high-functioning autistic and normally developing children as they perform tasks that selectively engage different linguistic and communicative abilities.

1:50 The Development of Auditory Processing as Examined by Electrophysiological and Magnetic Recordings

Elizabeth W. Pang (potential new member)

Director, EP/ERP Laboratories, Associate Scientist, Department of Paediatrics, University of Toronto, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada

An intact auditory processing system is thought to be one of the fundamental components in the learning of language. If auditory processing goes awry in the developing brain, devastating effects are often observed in the child’s ability both to learn, and to use, language. An understanding of the development of normal auditory processing, and examinations of whether certain language disorders show consistent patterns of auditory dysfunction, would provide great insight into how children acquire and become proficient at language and how this process malfunctions in different diseases. I will present normative ERP data examining the development of auditory processing in children. I will also present preliminary MEG data, from children tested in an auditory paradigm, to examine the localization of the neural generators underlying the developing auditory M100. Finally, I will present several examples of auditory recordings, both ERP and MEG, in children with known auditory and language processing deficits.

2:10 Facilitation Effects in Processing Visual Features in Adults and Children

M.J. Taylor and N.J. Lobaugh

CERCO – CNRS, Université Paul Sabatier, Toulouse, France, Cognitive Neurology Unit, Sunnybrook Health Sciences Centre, Toronto, Canada

We studied the influence of features (colour and form) and their conjunction on early stages of visual processing. Adults (n=27) and children (n=65, 7-12yrs, in three age groups) completed a series of tasks in which they detected targets as a function of shape and/or colour features, while ERPs were recorded. The targets differed for each task: in task #1, the target was discriminated by shape, colour was held constant; task #2, the target was discriminated by colour, shape was constant; task #3, the target required discrimination of a conjunction of features; task #4 (redundant task) the target could be discriminated using either feature or the conjunction of features. The N1 ERP component (at 175ms in adults) was very prominent at posterior temporal sites and was left-lateralised for adults when the feature of shape was required for the discrimination. In children, N1 latency decreased with age; the shortest latencies were also seen for conjunction targets. The colour task had shorter latencies than the shape task, suggesting greater ease with the feature of colour for the children, in contrast to adults. Across age groups N1 amplitude reflected attentional effects, as it was larger to targets than non-targets. Unlike adults, N1 generally showed a right-sided lateralisation in children, particularly for the colour task. Thus, both adults and children showed a facilitation effect for the conjunction task, the speed with which the stimuli were processed was faster when two features had to be utilised. Attentional effects were also seen in this early stage of visual processing. However, the distributional findings suggest that maturation of the processing of features and conjunctions of features is not complete by 12 years of age.

BREAK

3:00 Long-lasting Changes in Cortical Activity Following Object Naming

Miranda van Turennout1,2 (potential new member) and Alex Martin2

1Max Planck Institute for psycholinguistics, Nijmegen, The Netherlands. 2Laboratory of Brain and Cognition, National Institute of Mental Health, Bethesda, USA.

Naming an object once improves the ability to name that same object again. Behavioral studies have shown that speeded naming responses can be observed in normal individuals up to 48 weeks after a single exposure to an object, suggesting a permanent change. We used event-related fMRI to investigate the neural mechanisms underlying this long-lasting form of learning. Subjects named a series of briefly presented (200msec) pictures of objects at different time intervals (3 days, 6 hours, and 1 hour) before the scanning session. During the fMRI scanning session, subjects saw these pictures again, intermixed with novel pictures, and a repetition of the novel pictures after 30 seconds. Relative to a visual-noise baseline, naming objects activated a large network of cortical regions including posterior (bilateral ventral occipitotemporal), and anterior (left prefrontal and left insula) cortices. Activity in these regions was modulated by experience. We observed an immediate (30 sec) and long-lasting (3 day) decrease in neural activity in posterior regions following object repetition. In addition, slower developing decreases in left inferior frontal activity were observed concurrent with increases in left insula activity. These time-dependent changes suggest that experience-induced facilitation of object naming may be mediated by two distinct learning mechanisms: The formation of sparser, yet more object-form specific, representations in posterior regions, and experience-induced reorganization of the brain circuitry underlying lexical retrieval in anterior regions.

3:20 Getting a Grip on the Neural Substrates of Shape, Texture, and Hardness

Philip Servos

Department of Psychology, Wilfrid Laurier University,Waterloo, ON N2L 3C5, Canada

FMRI was used to investigate the neural substrates involved in haptic processing of texture, shape, and hardness. Subjects performed haptic classification tasks on a set of 27 silicone objects having parametrically defined shape, texture, and hardness. The objects were ellipsoids of revolution in which the ratio of the long to the short axis was varied, producing three different shapes. Three surface textures and three hardness levels were used. In three separate experiments, the same subjects classified each object along the three levels of one of the object properties (shape, texture, or hardness). Texture, shape, and hardness processing led to contralateral activation in the postcentral gyrus (PCG). A common region located within relatively posterior portions of the PCG was observed during shape and texture identification whereas a separate and more anterior region was activated during the hardness identification task. The hardness identification task also produced bilateral activation within the parietal operculum.

3:40 Multimodal Maps of Imitative Behavior

Marco Iacoboni (potential new member)

Assistant Professor of Psychiatry and Biobehavioral Sciences, UCLA School of Medicine, Ahmanson-Lovelace Brain Mapping Center, 660 Charles E. Young Drive South, Los Angeles, California 90095-7085,USA

Imitation is a powerful means of skill acquisition, social interaction, and transmission of culture in adulthood. In spite of the complexity of imitative behavior, even at birth we can imitate facial and some manual gestures. This built-in mechanism must be based on relatively simple neural mechanisms. One possibility is that imitative behavior is based on a direct matching mechanism of some sort of description of the observed action, either kinematic or pictorial, onto the internal mental representation of the same action. Recently, neurons with neurophysiological properties compatible with this mechanism have been described in the monkey inferior frontal cortex. We recently demonstrated that some cortical areas of the human brain are endowed with such a mechanism matching observation and execution of actions (Iacoboni et al, Science 1999). With the use of TMS and fMRI we recently addressed several questions related to action observation and imitation:1. Goals in imitative behavior: How does the presence of salient goals in the observed action affect the imitative process? 2. Intentionality: How do we understand the intentions of others through the observation and imitation of their actions? 3. Speech: Is the observation/execution matching system involved in speech comprehension? 4. How does visual experience affect corticospinal excitability during action observation? 5. How does the reference frame adopted by the observer affect the brain mechanisms involved in action observation and imitation? What emerges from these experiments is the central role of the mirror system as coordinator of human cortical areas associated with motor representation.

SHORT BREAK

4:20 The Organisation of Visual Object Representations: A Connectionist Model of Effects of Lesions in Perirhinal Cortex

Lisa M. Saksida (potential new member)

Department of Experimental Psychology, University of Cambridge, Cambridge, UK CB2 3EB

I will present a connectionist model, based on the configural model of Pearce (1994), of the organisation of object representations in the ventral visual stream, or “what” pathway linking occipital and temporal regions of the brain. The model is based on the assumption that representations in the ventral visual stream are organized hierarchically, such that representations of simple features of objects are stored in caudal regions of the ventral visual stream, and representations of the conjunctions of these features are stored in more rostral regions such as perirhinal cortex (PRh). We propose that a function of these feature conjunction representations is to help to resolve “feature ambiguity”, a property of visual discrimination problems that can emerge when features of an object are rewarded when part of one object, but not when part of another. Lesions in PRh are thus thought to impair the ability to resolve “feature ambiguity” in complex visual discriminations. In the first part of my talk, I will briefly describe the model and discuss how it can account for several recently reported effects of lesions of PRh. Next, I will describe two experiments that tested the specific prediction that PRh lesioned animals will be impaired on complex discrimination problems in which there is a high degree of feature ambiguity. In the first experiment, monkeys were tested on a series of concurrent discriminations in which the number of object pairs was held constant, but the degree of feature ambiguity was varied systematically. In the second experiment, monkeys were tested on single pair discriminations in which feature ambiguity across problems was varied systematically by “morphing” pairs of complex images together. The pattern of results in both experiments closely matched that predicted by simulations using the connectionist network: monkeys with PRh lesions were unimpaired under conditions of low feature ambiguity and were severely impaired under conditions of high feature ambiguity. The results of these simulations and the subsequent experiments suggest that effects of lesions in PRh on visual discrimination may be due not to the impairment of a specific type of learning or memory, such as declarative or procedural, but to compromising the representations of visual stimuli. Furthermore we propose that attempting to classify perirhinal cortex function as either “perceptual” or “mnemonic” may be misguided, as it seems unlikely that these broad constructs will map neatly onto anatomically defined regions of the brain.

4:40 Learning Associations: The Role of the Hippocampal System

V. Sziklas

Dept. Neurology & Neurosurgery, McGill University, Montreal, Canada

Rats with lesions of the fornix, the hippocampus, or normal control animals were trained on a visual-spatial conditional associative learning task in which they had to learn to go to a particular location based on the presence of a specific visual cue; the rats approached the cues from different directions. Animals with damage of the fornix were able to learn the task at a rate comparable to that of the control animals. The performance of the hippocampal rats was significantly impaired in comparison with that of the control group. To explore further the generality of the impairment in conditional learning after hippocampal damage, normal animals and those with lesions of the dorsal hippocampus were tested on a non-spatial visual-visual conditional associative learning task in which they had to learn to choose a particular object based on the presence of a specific visual cue. The rate of acquisition of rats with damage to the hippocampus was impaired in comparison with that of the control group on this task. These findings suggest that under certain conditions, a functional dissociation exists between the effects of damage to the fornix or the hippocampus and that, while the fornix may be only selectively involved in spatial learning and memory, the role of the hippocampus is a more general one.


Wednesday

9th Morning Session: _ Day Symposium

The Cingulate Cortices

John Aggleton

9:00 The Rodent Retrosplenial Cortex: The Forgotten Link to the Hippocampus

John P. Aggleton

School of Psychology, Cardiff University, Po Box 901, Cardiff, Wales UK CF10 3YG

The retrosplenial cortex occupies a pivotal position, linking the hippocampal formation with other limbic regions. While much attention has focussed on the roles of the parahippocampal cortices as critical inputs to the hippocampus, the contribution of the retrosplenial cortex has been largely overlooked. In a series of neurotoxic lesion studies in rats we found that lesions of the rostral retrosplenial cortex had no apparent effect on the performance of spatial tasks sensitive to hippocampal lesions. This was surprising given the increase in retrosplenial cortex activity, as measured by Fos expression, that occurs during the same tasks. A subsequent experiment therefore examined the effects of complete retrosplenial lesions, and this produced robust deficits on an array of spatial tasks. These deficits were larger than those associated with combined perirhinal/postrhinal lesions, emphasizing the potential importance of this region for hippocampal function.

9:45 Anterior Cingulate Cortex of the Primate: Where Motor Control, Drive and Cognition Interface.

Tomá_ Paus, Department of Neurology & Neurosurgery, McGill University, Montreal Neurological Institute, 3801 University Street, Montreal, QC, H3A 2B4 CANADA

The last decade saw a surge of interest in the structure and function of the anterior cingulate cortex (ACC) in human and non-human primates. Three key features dominate current discussions on the role of the ACC in behavioural control. First, dense projections from the ACC to the motor cortex and spinal cord seem to implicate this region in motor control. Second, reciprocal cortico-cortical connections of the ACC with the lateral prefrontal cortex appear to support its proposed role in decision making. Third, extensive afferents from the midline thalamus and the brainstem nuclei suggest that changes in emotional and motivational states can also lead to ACC engagement. Here I attempt to integrate these new findings with an old concept, namely that of willed control of actions.

BREAK

11:00 The role of cingulate and prefrontal cortex in associative learning in the rat.

Timothy J. Bussey (potential new member)

University of Cambridge, Department of Experimental Psychology

I will describe a series of experiments investigating the role of the anterior cingulate, posterior cingulate (retrosplenial) and medial prefrontal cortices in associative learning in the rat. I will present evidence from lesion experiments indicating a triple functional dissociation between these three cortical regions. Briefly, medial prefrontal lesions impaired reversal learning and attentional function, posterior cingulate lesions impaired tasks requiring the use of S-R associations, and anterior cingulate lesions impaired tasks requiring the acquisition of stimulus-reward associations. Subsequent experiments revealed that involvement of the anterior cingulate cortex is not essential for all forms of stimulus-reward learning, but instead makes a specialised top-down contribution to an amygdalo-striatal circuit important for basic “emotional” learning.

11:45 Functional Subdivision in the Medial Frontal and Cingulate Cortices

Matthew Rushworth, Department of Experimental Psychology, University of Oxford,

South Parks Road, Oxford, OX1 3UD, England, UK

The medial wall of the primate frontal lobe consists of different reas. Recent investigations of the human and macaque medial frontal cortex using fMRI, TMS, and lesions have begun to reveal the distinct functional contributions of three areas: the anterior cingulate gyrus, the anterior cingulate sulcus, and the superior frontal gyrus. Functional neuroimaging experiments have suggested medial frontal and cingulate involvement in cognitive processes such as task switching. In a combined fMRI and TMS experiment, however, it is clear that medial frontal and cingulate cortex is only critical when task switching requires subjects to manipulate the way in which they select responses; the cognitive role of these regions is related to their motor functions. An area in the superior frontal gyrus, the pre-SMA, is important for switching between tasks that require different response sets and its role can be distinguished from that of the premotor cortex in selecting individual responses. The cingulate sulcus is activated in similar situations, but lesions in this area in the macaque brain do not impair task switching. Instead the performance of monkeys with lesions are consistent with a role for anterior cingulate sulcus in reward and error guided response selection. The anterior cingulate gyrus does not seem to be involved in such motor related and cognitive processes. Lesions in this region affect social behaviour. The deficit is distinct to that seen following amygdala lesions because fear related behaviour is relatively unimpaired while social and affiliative behaviour is impaired.

Wednesday 12:30 PM BUSINESS MEETING OVER LUNCH

Wednesday afternoon and evening: Outing and dinner

Presidential Speaker: Nadia KADRI, M.D.

Professor of Psychiatry

University Psychiatric Center, Faculty of Medicine, University Hassan Second, Casablanca, Morocco

Cross Cultural Differences in Psychiatric Diagnosis, Treatment and Societal Attitudes

Time and location to be announced