Ch. 4 Definitions - Hemispheric Specialization

Anterior commissure

The nerve bundle connecting the left and right cerebral hemispheres that is located anterior to the corpus callosum

Cerebral specialization

The adaptation of the activity in a particular brain region to subserve a given cognitive function or behavior

Commissures

White matter tracts that cross from the left to the righ side, or vice versa, of the central nervous system. The corpus callosum is the largest one.

Corpus callosum

A fiber system composed of axons that connect the cortex of the two cerebral hemispheres. It is the largest white matter structure in the brain. 

Dichotic listening task

An auditory task in which two competing messages are presented simultaneously, one to each ear, while the participant tries to report only one or both messages.The ipsilateral projections from each ear are presumably suppressed when a message comes over the contralateral pathway from the other ear.

Functional asymmetry

A difference in the functions that each hemisphere subserves 

Handedness

The tendency to perform the majority of one’s manuall actions with either the right or left hand. 

Heterotopic areas

Noncorresponding areas of the brain. Usually have connections with one another.

Heterotopic connections 

Connections from one region that travel within the corpus callosum to a different region in the opposite hemisphere

Hierarchical structure

A configuration that may be described at multiple levels, from global features to local features; the finer components are embedded within the higher-level components

Homotopic areas

Areas in corresponding locations in the two hemispheres

Homotopic connections

Connections from one region that travel within the corpus callosum to a corresponding region in the opposite hemisphere 

Interpreter

A left-hemisphere mechanism that seeks explanations for internal and external events in order to produce appropriate response behaviors

Modules 

Specialized, independent, and frequently localized networks of neurons that serve a specific function 

Planum temporale

The surface area of the temporal lobe that includes Wernicke’s area. Long been believed to be larger in the left hemisphere because of the lateralization of language function (controversial theory)

Posterior commissure

The nerve bundle connecting to the left and right cerebral hemispheres that is located posterior to the corpus callosum. Contains fibers that contribute to the pupillary light reflex

Splenium

The posterior portion of the corpus callosum. It interconnects the occipital lobe.

Sylvian fissure

A large fissure on the lateral surface of the cerebral cortex which separates the frontal cortex from the temporal lobe below

Wada test

A clinical procedure in which amobarbital is injected to temporarily disrupt function in one of the cerebral hemispheres. Used to identify the source of epileptic seizures and provided important initial insights into hemispheric specialization