JOBB FÉLTEKE DOMINANCIA A VIZUÁLIS STATISZTIKUS TANULÁS KEZDŐFÁZISÁBAN

1. JOBB FÉLTEKE DOMINANCIA A VIZUÁLIS STATISZTIKUS TANULÁS KEZDŐFÁZISÁBAN József Fiser, Matthew E. Roser*, Richard N. Aslin# & Michael S. Gazzaniga* Brandeis University, University of Rochester# and Dartmouth College*

2. Great diversity of proposed hemispheric specializations

3. Hemispheric differences in object perception • For highly familiar objects: • RH  metric and positional information LH  abstract categorical information • RH  visual form information • LH  conceptual associations • RH  early information (low SF) • LH  late information (high SF)

4. Left hemisphere Right hemisphere Object perception requires visual feature learning • First, visual scenes are interpreted via already learned object features • Next, search for new specific spatial co-occurrences and new arrangements among elements (emergence of new feature combinations) occurs • Finally, explicit access to a new feature by developing associations and categorical and semantic meaning

5. Question: Can the process of learning new visual features be linked to differential involvement of the two brain hemispheres?

6. Six base-pairs Fit three base-pairs into 3 X 3 grid The basic paradigm Visual feature = spatio-temporal conjunction of separate shapes

7. A F B E I J A B F I Testing phase • 2AFC task • Base-pair vs. Non-base pair Base-pair Non-base pairs

8. 2 deg Modifying the paradigm Split the base-pairs

9. Modified test phase Four lateralized test types Ipsilateral: • Practice: RH Test: RH • Practice: LH Test: LH Contralateral: • Practice: RH Test: LH • Practice: LH Test: RH

10. Rostrum Splenium (Corballis et al. Neurology 2001) Subjects • Normal subjects: Sixteen college students • Callosotomy patient: V. P.

11. Experimental procedure for normal subjects • Practice: • 144 scenes alternating randomly between the right and left visual fields • Eye-movements monitored by iView to verify fixation (and hemifield stimulation) • Test: • Six test trials in each of the four test types (Ipsi, Contra) x (RH, LH)

12. Results with normal subjects Chance Equal learning in all conditions  interhemispheric transfer

13. V.P.'s testing schedule Data collection in five days 1st day: practice 2nd day: practice, ipsilateraltests, practice, ipsilateral tests 3rd day: practice, ipsilateral tests, practice, ipsilateral tests 4th day: practice, contralateral tests 5th day: practice, contralateral tests

14. Results with the split brain patient * Chance • Contralateral: No interhemispheric information transfer • Ipsilateral: Strong right hemisphere advantage

15. Conclusions • Visual statistical learning does not transfer across split hemispheres even when some limited transfer of higher-level word-related information is possible • The initial phase of extracting spatial statistical regularities from the visual input is dominated by right hemisphere processes • These results predict a shift of relative brain activity from the right to the left hemisphere as visual perception shifts from naïve observation to a knowledge-based interpretation of the scene