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Toward a Deeper Understanding of the Involvement of the Caudate Nucleus in Perceptual Category Learning

J. Scott Lauritzen & W. Todd MaddoxInstitute for Neuroscience and Department of Psychology, The University of Texas at Austin

Introduction•Procedural learning based system mediates learning of “non-verbalizable” category structures [1]

3. Summary

References

http://homepage.psy.utexas.edu/homepage/Group/MaddoxLAB/

[1] Maddox, W.T., Ashby, F.G.  (2004).  Dissociating Explicit and Procedural-Learning Based Systems of Perceptual Category Learning.  Behavioral Processes.  66, 309-332.

[2] Nomura, E.M., Maddox, W.T., Filoteo, J.V., Ing, A.D., Gitelman, D.R., Parrish, T.B., Mesulam, M-M., Reber, P.J. (Under Review). Neural Correlates of Rule-Based and Information-Integration Category Learning.

[3] Seger, C.A., Cincotta, C.M. (2005). The Roles of the Caudate Nucleus in Human Classification Learning. The Journal of Neuroscience. 25(11), 2941-2951.

[4] Saint-Cyr, J.A., Ungerleider, L.G., Desimone, R. (1990). Organization of Visual Cortical Inputs to the Striatum and Subsequent Outputs to the Pallido-Nigral Complex in the Monkey. The Journal of Comparative Neurology. 298(2), 129-156.

[5] Wilson, C.J. (1995). The Contribution of Cortical Neurons to the Firing Pattern of Striatal Spiny Neurons. (pp. 29-50). Cambridge, MA: MIT Press.

[6] Yeterian, E.H. & Pandya, D.N. (1998). Corticostriatal Connections of the Superior Temporal Region in Rhesus Monkeys. The Journal of Comparative Neurology. 399, 384-402. General Methods

Key Concepts•Caudate nucleus receives “many-to-one” convergence of input from perceptual areas [4]

•Differential input into the caudate nucleus across sensory modalities [5,6]

•Visual input exclusively into tail [5]

•Auditory input into head, body, and tail [6]

•Hypothesis: Perceptually dissimilar items project to different functional units in the caudate, adversely affecting “non-verbal” category learning.

192.10

•Human participants view a series of images and categorize each image

•“Non-verbal” category learning is impaired by discontinuous category structures and cross-modal stimuli

•The locus of the effects for discontinuous & modality experiments are different

•Deficits with discontinuous stimuli appear to be due to sub-optimal caudate unit recruitment

•With cross-modal stimuli many participants employ an incorrect (hypothesis-testing) strategy or resort to random responding

1. Discontinuity Effects

Category Structure

Results

•Prediction: Discontinuous category structures should impair “non-verbal” category learning relative to continuous category structures

•Discontinuous categories impair learning

•Caudate has difficulty associating perceptually distinct stimuli with the same response

PFC=Prefrontal Cortex GP=Globus Pallidus SN=Substantia Nigra Thal=Thalamus

H=Head of Caudate B=Body of Caudate T=Tail of Caudate

2. Modality Effects

Results

Category Structure•Identical stimulus values used for generation of 3 types of stimuli

•Each stimulus type pairs different relevant stimulus dimensions

•Prediction: Across-modality stimuli should impair “non-verbal” category learning relative to within-modality stimuli

•Participants displayed deficits with cross-modal stimuli relative to within-modal stimuli

•Differential sensory input to the caudate nucleus may account for the observed deficits

Abstract•Two experiments provide empirical evidence that differential perceptual stimuli impair learning of “non-verbalizable” category structures

SUBJECT RESPONSESTIMULUS FEEDBACK

CORRECT

FIXATION

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•Continuous stimulus values are immediately adjacent

•Discontinuous stimulus values introduce within-category separation

Caudate Nucleus

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The caudate nucleus, in conjunction with other structures, mediates “non-verbal” category learning [2,3]

Acknowledgements:

This research was supported in part by National Institute of Health Grant R01 MH59196 to WTM, and a McDonnell-Pew Consortium Grant.