Hemispheric Specialization I

Goals for Today’s Class:

   Understand basic concepts of neuropsychology Discuss lateralization/localization of function in the human brain Study hemispheric specialization

Lateralization

 The two different cerebral hemispheres (halves of the brain) DO differ  The hemispheres are connected via the

corpus callosum

Common Myths

   There is a lot of “pop psychology” about hemispheric specialization Broad statements like ‘the left brain is logical and the right brain is creative’ are almost always gross over-generalizations The two hemispheres do NOT operate independently; they communicate constantly, mostly via the corpus callosum

Lateralization

 different parts of the brain have different functions  => localization of function  left and right hemispheres are specialized to do different things  => this is known as lateralization.  contralaterality—the right half of your brain controls the left half of your body and vice versa.

Left visual field (LVF) Right visual field (RVF) Left Hemisphere Right Hemisphere

Some True Differences

 Left Brain    Controls the right side of the body Tends to be better suited for language Receives input from the RIGHT visual field  Right Brain    Controls the left side of the body Tends to be better suited to spatial tasks Receives input from the LEFT visual field

Visual Field Hemisphere Function

R L

Language

L R

Spatial Tasks

How can we study the differences between hemispheres?

 Cut corpus callosum of severe epileptics L/R hemispheres will not communicate as quickly as those in normal people OR . . .

We could restrict information to either the left or right hemisphere

Overview of Experiment

     Q: is the left hemisphere better-suited for language processes or not?

Stimuli: 40 words and 40 nonwords Half of the stimuli are 3 letters long, the other half 6.

Half of the items are presented to the LVF/RH and half to the RVF/LH.

Words randomly assigned to conditions.

words(40) non-words(40) 3-letters (20) 6-letters (20) 3-letters (20) 6-letters (20) LVF (10) RVF (10) LVF (10) RVF (10) LVF (10) RVF (10) LVF (10) RVF (10)

Design:

     IV1: lexicality  with 2 levels: word or nonword IV2: field of presentation  with 2 levels: RVF or LVF IV3: number of letters  with 2 levels: 3- or 6 letters DV1: reaction time DV2: error rate in %

Instructions:

   to begin a trial press the "space bar".

Focus on X.

respond as fast as possible, but also try to avoid making errors.