Split-brain

A similar effect occurs if a split-brain patient touches an object with only the left hand while receiving no visual cues in the right visual field; the patient will be unable to name the object, as each cerebral hemisphere of the primary somatosensory cortex only contains a tactile representation of the opposite side of the body.

If the speech-control center is on the right side of the brain, the same effect can be achieved by presenting the image or object to only the right visual field or hand.

[4] In 1936, Dandy described three cases in which he cut the corpus callosum from its posterior (towards the back of the head) across about two thirds of its width.

For example, people with lesions in two specific areas of the left hemisphere lost their ability to talk, to read, and to understand speech.

Even though Sperry is considered the founder of split-brain research, Gazzaniga's clear summaries of their collaborative work are consistently cited in psychology texts.

The subject was told to sit in front of the board and stare at a point in the middle of the lights, then the bulbs would flash across both the right and left visual fields.

Questioning this result, the researchers found that the subjects could later match it from several similar objects; tactile sensations limited to the right hemisphere were accurately perceived but could not be verbalized.

[7] Sperry and Gazzaniga went on to conduct other tests to shed light on the language processing abilities of the right hemisphere as well as auditory and emotional reactions as well.

One's left hemisphere of the brain is thought to be better at writing, speaking, mathematical calculation, reading, and is the primary area for language.

The right hemisphere is seen to possess capabilities for problem solving, recognizing faces, symbolic reasoning, art, and spatial relationships.

In the mid-1980s Jarre Levy, a psychobiologist at the University of Chicago, was at the forefront of scientists who wanted to dispel the notion we have two functioning brains.

Another study by Parsons, Gabrieli, Phelps, and Gazzaniga in 1998 demonstrated that split-brain patients may commonly perceive the world differently from the rest of us.

On the other hand, the left hemisphere controls the primary sensory functions of the right side of the body and is responsible for scientific and math skills, and logic.

This structure is composed of white matter: millions of axons that have their dendrites and terminal boutons projecting in both the right and left hemisphere.

[14] This organization results in modality-specific regions of the corpus callosum that are responsible for the transfer of different types of information.

[17] A model proposed by Iacoboni et al.[18] suggests split-brained patients experience asynchronous activity that causes a stronger signal, and thus a decreased reaction time.

There is little functional plasticity observed in partial and complete callosotomies on adults; the most neuroplasticity is seen in young children but not in infants.

This suggests that posterior callosal sections that include the hippocampal commissures cause a mild memory deficit (in standardized free-field testing) involving recognition.

[29] In general, split-brained patients behave in a coordinated, purposeful, and consistent manner, despite the independent, parallel, usually different, and occasionally conflicting processing of the same information from the environment by the two disconnected hemispheres.

This is due to the compensatory phenomena; split-brained patients progressively acquire a variety of strategies to get around their interhemispheric transfer deficits.

[36] The surgical operation to produce this condition (corpucallosotomy) involves transection of the corpus callosum, and is usually a last resort to treat refractory epilepsy.

He was a World War II paratrooper who was injured at 30 years old during a bombing raid jump over the Netherlands, and again in a prison camp following his first injury.

During his surgery in 1962, his surgeons determined that no massa intermedia had developed, and he had undergone atrophy in the part of the right frontal lobe exposed during the procedure.

[verification needed]Funnell et al.'s (2007) experiments were to determine each of JW's hemisphere's ability to perform simple addition, subtraction, multiplication and division.

For example, in one experiment, on each trial, they presented an arithmetic problem in the center of the screen for one second, followed by a central crosshair JW was to look at.

After one more second, Funnell et al. presented a number to one or the other hemisphere / visual field for 150 ms—too fast for JW to move his eyes.

Turk et al. concluded there are cortical networks in the left hemisphere that play an important role in self-recognition.

The first experiment was designed to assess VP's ability to make between-field perceptual judgments about simultaneously presented pairs of stimuli.

The stimuli were presented in varying positions with respect to the horizontal and vertical midline with VP's vision fixated on a central crosshair.

[citation needed] A second experiment involving VP attempted to investigate what aspects of words transferred between the two hemispheres.