Studies on cognitive processes of the brain

Studies on cognitive processes of the brain include those on:

Aphasia

Aphasia is often caused by brain damage, and refers to the inability to understanding the content of speech and/or produce speech. There are numerous kinds of aphasia, two of which are Broca’s aphasia and Wernicke’s aphasia.

Broca’s area

Broca’s area is located in the left frontal lobe (in the prefrontal cortex). It is responsible for the production of language and speech, specifically the movement of the muscles in the face which allows one to speak. Damage to Broca’s area may lead to Broca’s aphasia:

Broca’s aphasia

An individual experiencing Broca’s aphasia would have difficulty in the physical processes of producing speech. Whilst the individual may be capable of producing a few words (mainly simple content words), a lot of mental effort would be required. Broca’s aphasia does not impact comprehension of language, meaning that a sufferer would be capable of understanding what you have said, capable of thinking about how they want to reply, but incapable of actually producing those words. An individual suffering from Broca’s aphasia is highly likely to be aware of their condition.

Wernicke’s area

Wernicke’s area is usually located in the left temporal lobe, however it may be present in the right temporal lobe at times (more likely for left handers). It is responsible for the comprehension of language and speech, specifically using the correct words at the correct time. Damage to Wernicke’s area may lead to Wernicke’s aphasia:

Wernicke’s aphasia

An individual experiencing Wernicke’s aphasia would have difficulty in the sensical comprehension of language. Whilst the individual’s physical production of speech is unaffected and their speech remains fluent, they are incapable of linking together words or ideas in a logical way. Subsequently, the content of their speech may be non-sensical and very confusing. An individual suffering from Wernicke’s aphasia is unlikely to be fully aware of their condition, meaning that they may believe that they understand or that they are making sense when, in reality, they are not.

Broca’s area and Wernicke’s area are roughly shown on the diagram below.

broca wernicke

Spatial neglect

Spatial neglect refers to a phenomenon in which an individual consistently ignores stimuli presented from one side of the body. Although some sufferers are aware of their condition, others are entirely oblivious.

Further to only recognising senses from one side of the body (i.e. only seeing, hearing etc. half of what they should), individuals suffering from spatial neglect may experience reconstructed memories, whereby they only recall sensory information from one side of memories.

Spatial neglect is mainly caused from damage in the right parietal lobe, meaning that the left sensory side is neglected more often than the right.

Split-brain studies

The effects of lateralisation (one hemisphere being more dominant than the other in regard to specific tasks) were made clear by split-brain studies. Individuals who had undergone surgery to remove their corpus callosum, thereby separating the two hemispheres in their brain, were used as subjects.

Roger Sperry and Michael Gazzaniga

Sperry and Gazzaniga used split-brain subjects to test the effects of lateralisation. To do this, they provided visual information to either the left or the right visual field (the left visual field refers to the left half of each eye, and the right visual field the right half of each eye) of their subjects. As the subjects’ hemispheres in their brains had been separated, information provided to the left visual field could only be processed in the right hemisphere of the brain, and vice versa. The responses of the subjects, then, provided great insight into the specific functions of each hemisphere.

In general, subjects were capable of verbally explaining what they saw when the information was presented to their right visual field (and processed in their left hemisphere). Conversely, subjects were incapable of doing so when the information was presented to their left visual field (and processed in their right hemisphere). When this was the case, subjects were only capable of portraying what they saw non-verbally, using actions or drawings.