Penfield's Study of The Interpretive Cortex

Wilder Penfield

Wilder Penfield was a famous American-Canadian Neurosurgeon who opened the Montreal Neurological Institute and Hospital and carried out pioneering research that paved the way for Neuroscience. Quite a lot of his research was carried out on Epilepsy patients, and his research advanced our knowledge of brain functionality.

Let's start by learning about the Wilder Penfield brain map and the contributions it made to Neuroscience.

Wilder Penfield Brain Map

Let's start by figuring out what exactly is meant by brain mapping in psychological research. Brain mapping is a research domain that involves identifying brain structures and their associated functions.

This may sound strange as Wilder is a famous Neurosurgeon who pioneered Neuroscience. One of his most notorious research is when he mapped the cerebral cortex on two models representing motor and sensory homunculus.

Fig 1 - The Homunculus brain map shows which part of the sensory-motor influences which body part.

So now we know what Penfield did, let's now delve into how he mapped the motor cortex.

As Penfield treated his patients with epilepsy (he did actually help the majority of his patients alleviate their symptoms), he mapped the architecture of the cortex using the Montreal Procedure.

• The procedure aims to identify the region causing the seizures and remove it.

The brain has no pain receptors, so the patients stayed awake during the procedure; Penfield passed small and safe electrical currents (tDCS) to the patient's exposed brain. During the procedure, he observed that passing electrical impulses in different areas evoked responses in different body parts, e.g. numb fingers; this is how Penfield mapped the brain region and which body part it affected.

Going back to his epilepsy patients, before having a seizure, people with epilepsy usually have a feeling; this may be a specific smell, taste or feeling. When Penfield found the brain area that evoked the same feeling, he removed it, reducing the likelihood of seizures occurring again in the future.

Penfield's Study of the Interpretive Cortex Aim

Now that we have a little background information on who Wilder Penfield is let's look at one of his studies, the study of the interpretive cortex. The study aimed to identify the psychological consequences of stimulating various parts of the temporal cortex using the Montreal Procedure. The Montreal Procedure is used to treat patients with epilepsy surgically.

Penfield's Study of the Interpretive Cortex Method

The study recruited clinical case trials of individuals undergoing open brain surgery to alleviate their epilepsy symptoms. The study occurred in a clinical hospital setting, and patients were required to stay awake during the surgery.

The study involved the surgeon passing a small, safe electrical current to excite neurons in the different areas of the exposed temporal lobe using the Montreal Procedure.

The study collected qualitative data as the patients were asked to describe what they experienced and felt during the surgery.

The study tried to identify if the location of temporal lobe stimulation (the independent variable) affected patients' descriptions of their past experiences (the dependent variable).

Penfield's Study of the Interpretive Cortex Results

Penfield found that stimulating specific neurons in the temporal lobe led to patients visualising past experiences, and the stimulation of other neurons led patients to relive emotions evoked during past experiences, such as fear or disgust.

Interestingly, Wilder Penfield found that patients heard and felt emotions concerning past memories when electrical currents passed through either side of the temporal cortex. But, patients (except one) described visually seeing features of past memories (e.g. dimension, objects seen and distance) during activation of their non-dominant temporal cortex.

An example of a response that a participant gave during the procedure is...

From Penfield's study of the interpretive cortex results, it can be concluded that parts of the temporal lobe play a role in storing facts and memories of past experiences and other parts of emotions evoked during such experiences.

Additionally, the Penfield study highlights that brain regions are associated with specific functions, also known as brain functionality.

Penfield's Study of the Interpretive Cortex Overview

To consolidate your learning, let's quickly summarise what Penfield did and found in his study of the interpretive cortex.

• The study aimed to identify the psychological effects of stimulating various parts of the temporal cortex using the Montreal Procedure.
• The study took place in a clinical hospital setting on epilepsy patients undergoing open brain surgery.
• The study tried to identify if the location of temporal lobe stimulation (the independent variable) affected patients' descriptions of their past experiences (the dependent variable).
• Penfield found that stimulating specific neurons in the temporal lobe led to patients visualising past experiences, and stimulating other neurons led patients to relive emotions evoked during past experiences, such as fear or disgust.
• From Penfield's study of the interpretive cortex results, it can be concluded that parts of the temporal lobe play a role in storing facts and memories of past experiences and other parts in the emotions evoked during such experiences.

Penfield's Study of the Interpretive Cortex Evaluation

Let's now discuss some of the strengths and weaknesses of Penfield's study of the interpretive cortex.

Penfield's Study of the Interpretive Cortex: Strengths

One of the benefits of the Penfield study was that he occasionally used his patient's as controls. In research, we use control measures to increase the validity of the research. In this study's case, if the researcher found that the participants were being truthful, then the study had high internal validity.

Another strength of the study is its reliance on tDCS to activate brain regions. The advantage of using this neuro-stimulating technique is that it can accurately activate neurons in specific regions; this means the study measures what it intends to, thus increasing the study's internal validity.

As the study used a qualitative design, Penfield collected detailed accounts that allowed him and other researchers to understand the participant's experiences during the study.

Moreover, as the study recruited patients receiving open surgery, they had to be consciously awake so that ethical reasons, such as psychological and physical harm, were not breached.

Penfield's Study of the Interpretive Cortex: Weaknesses

A weakness of the study is that it was carried out on patients with epilepsy; these findings may not apply to people who do not suffer from epilepsy. Therefore, the study can be criticised for using a non-representative sample, which makes it difficult to generalise and make inferences about the population.

Another weakness of the study is that it relied on qualitative data, so no statistical findings were reported; this also makes it difficult to make inferences concerning the population.