Mapping the mind: Exploring the Brain's function

Do you think that our brain functions are interconnected or restricted to one place of our brain?

In psychology, there are 2 theories to answer this question. 

The first is the holistic theory. This means that our brain functions is interconnected. Plasticity can show this (we'll discuss this more later). The second is the localisation of function. This is the theory that different areas of the brain are responsible for different behaviours, processes or activities. 

Before Broca and Wernicke (2 psychologists who studied speech) discovered that specific areas of the brain are associated with physical and psychological functions, scientists supported the holistic theory of the brain. 

Localisation of function (a.k.a cortical specialisation) is the idea that if we damage an area of our brain, the function will also be affected, because different parts of the brain perform different tasks and are involved with different parts of the body. 

Brain hemispheres

What is lateralisation?

It's that 2 halves of the hemispheres are functionally different and each hemisphere has functional specialisations

Can I tell you something crazy? The activity on the left side of the body is controlled by the right hemisphere and the activity on the right side of the body is controlled by the left hemisphere. 

The cerebral cortex is the outer layer of both hemispheres and covers the inner part of the brain. It is 3mm thick and is a lot more developed than other animals. Separating us- from them. Grey matter is the brains outer layer and describes the surface appearance of the brain because the cortex appearances due to a high concentration of neuronal cell bodies.

4 lobes, subdivided in the cortex of both hemispheres

The pink section. 

• Frontal lobe
• Back of the frontal lobe is the motor area
• Motor area controls voluntary movements in opposite sides of the body. 
• Damaged motor area results in a loss of control over fine movement

Central sulcus, it's not in this photo, but separates the motor area from the somatosensory area. 

It's a valley or a boundary between the two. 

The blue section. Let's understand it. 

• Parietal lobe
• Front of the parietal lobe is the somatosensory area
• Somatosensory area is where sensory information from the skin is received and sensations like pain, pressure and heat are represented. 
• The amount of sensory input is received relative to other areas is how much the somatosensory area is devoted to that region

The orange section. Can you see it?

• Occipital lobe
• Back of the brain is the visual area/cortex
• Again, with the crazy fact above, information from the left visual field will be sent to the right visual cortex and any information from the right visual field will be sent to the left visual cortex. 
• Damage to the left hemisphere for example can cause blindness to the right visual field of both eyes 

The green section. Let's talk about it.

• Temporal lobe
• Within this is the auditory area
• Auditory area analyses speech-based information 
• Damage causes partial hearing loss. More extensive damage, more extensive the loss. Could also affect ability to comprehend language 

Broca's area and Wernicke's area

Language is only found in the left side of the brain. 

1880s, Broca: small area in the left frontal lobe responsible for speech production. 

Damage to Broca's area can cause Broca's aphasia.

Broca's aphasia: Slow speech lacking in fluency

Wernicke: severe difficulties understanding language, but no problem producing language. So they'd be fluent but meaningless

Damage to Wernicke's area (left temporal lobe) causes Wernicke's aphasia

Wernicke's aphasia: nonsense words (neologisms) as part of their speech

Brain scanning evidence supporting localisation

In 1988, Petersen et al used brain scans. 

He found that Broca's area was active during reading tasks and Wernicke's area was active during listening tasks. So both areas of the brain has different functions. 

In 1994, Tulving et al studied long-term memory. 

He found that in different parts of the prefrontal cortex, semantic and episodic memories are found. 

Neurosurgical evidence: lobotomy

Lobotomy is severing connections in the frontal lobe to control aggressive behaviour. Unethical and imprecise, in 1950s, surgically removing or destroying areas of the brain to control behaviour was a thing. 

Used today is neurosurgery in OCD and depression. 

In 2002, Dougherty et al, had 44 OCD patients who has undergone a neurosurgical procedure which lesioned the cingulate gyrus. After 32 weeks, 1/3  had a successful response to the surgery and 14% had a partial response. Therefore symptoms and behaviours of severe mental disorders are localised. 

Lashley's research

Lashley removed 10-50% of cortexes in the rats brains who were learning the maze. No area was more or less important in the rat's ability to learn the maze. Every part of the cortex was required to learn it. So learning is to complex to be localised, and involvement of the whole brain is required. 

Cortex = the outer layer of the cerebrum (the cerebral cortex ), composed of folded grey matter and playing an important role in consciousness.