The Thinking Brain - Part 3 - Putting it all together

Over the past few weeks, we have been looking at The Thinking Brain (The Cerebral Cortex).

We examined how we sense things in our environment, both visual and auditory, and how we move our body in response to them.

This week we will look at the association areas which intervene between the sensory inputs and motor outputs and perform high-level integration tasks.[i]

When we perceive an object, our brains perceive a single option from all our senses. How this happens is called the binding problem.

Originally, researchers thought that information converged into the association areas.

However, more recent research has found that the association areas perform advanced processing in vision or hearing.[ii]

But that leaves the question of how senses are associated with each other. For all we have learned about the brain, somethings are still a mystery.

While researchers cannot fully explain why this happens, we know that it does happen from experiments and from people who, unfortunately, are unable to do some associations.

Binding in Action

Here are some examples demonstrating this.

When we watch a ventriloquist, we associate the sound from the ventriloquist with the movement of the dummy’s mouth.[iii] Contrast this with watching a badly dubbed foreign movie where the lips don’t move at the same time as the speech and you perceive that the words are not coming from those lips.[iv]

Photo by Siri Stafford/Photodisc / Getty Images

You can examine this yourself. If you see a light flash once while hearing two beeps, you can sometimes think the light flashed twice. If the tone is soft, the opposite can happen.[v]

Another way is through the following demonstration.

• Sit next to a large mirror so that you can see your right hand in the mirror. Keep your left hand out of sight.

• Squeeze your and release both hands in unison.

• Wiggle your fingers and touch your thumb to each finger with both hands at the same time.

• Because you feel your left hand doing things while seeing the reflection of your right hand in the mirror.

• After a few minutes, you can start to feel that the mirror hand is your own left hand.

When things go wrong

One of the other ways we know that binding takes place is in cases when it goes wrong.

Prosopagnosia – An inability to recognise faces

When people have issues with their visual posterior association area, it can result in them not being able to recognise familiar faces. This is called prosopagnosia.

This has nothing to do with their vision.

They CAN

• Identify a face is a face and the parts of a face.

• Identify emotions from facial expressions, however,

They CANNOT

• Identify a face of a particular person including recognising their relatives and sometimes even their own face.[vi]

Photo by funky-data/iStock / Getty Images

Associative Agnosia – An inability to name objects they see

Another example is when there are issues with the posterior parietal cortex.

People with this issue can draw and perceive objects but CANNOT name them. This is known as associative agnosia.[vii]

They can name the object if they touch them but not from an image.

https://agnosia-ot.weebly.com/categories-of-agnosia.html

Apperceptive Agnosia – An inability to draw objects

In the opposite case, damage to the occipital lobes can lead to people being able to name an object but not draw them (apperceptive agnosia).[viii]

https://agnosia-ot.weebly.com/categories-of-agnosia.html

Contralateral Neglect – Missing half of the world

This is one of the more dramatic examples of issues with associative areas.

When people have damage to the right posterior parietal visiocortex, then can end up neglecting the left part of the world. This can result in them:

Completely ignoring the left side of objects and their body – contralateral neglect syndrome,

No washing or dressing the left side of their body – personal neglect syndrome, and

Disowning the left side of their body to the extent where they remark, ‘Who put this arm in my bed?’ when they see their left arm.

From F. E. Bloom and A. Lazerson. (1988) cited in https://www.semanticscholar.org/paper/The-Parietal/244636d6101393aeaf29593a352cbdb180bff1ca/figure/7

However, it is not that they cannot sense the left part (it is not a sensory problem).[ix]

In a study, people were asked to imagine themselves at famous landmark (the Piazza del Duomo Public Square). 

• When they imagined themselves facing the cathedral in the square, they could recall only the buildings on their imagined right.

• However, when they imagined themselves at the cathedral looking out at the square (facing the opposite direction), they could still only recall the buildings on their imagined right (which were the same building they were unable to recall in the first activity).

• So they knew all of the buildings but what they could recall was dependent on which way the imaginedthemselves standing.[x]

Conclusion

When we perceive an object, our brains perceive a single option from all our senses. How this happens is called the binding problem. While researchers cannot fully explain why this happens, we know that it does happen. We can demonstrate how our brain associates inputs and we can also see what happens when brain damage occurs and association does not occur. So while we know that we bind two experiences that occur at the same time, we are still unsure about how exactly we to this.

[i] https://nba.uth.tmc.edu/neuroscience/m/s4/chapter09.html

[ii] Blanke, 2012 cited in Kalat, J. W. (2015). Biological psychology. Nelson Education.

[iii] Kalat, J. W. (2015).

[iv] Kalat, J. W. (2015).

[v] Kalat, J. W. (2015).

[vi] https://nba.uth.tmc.edu/neuroscience/m/s4/chapter09.html

[vii] https://nba.uth.tmc.edu/neuroscience/m/s4/chapter09.html

[viii] https://nba.uth.tmc.edu/neuroscience/m/s4/chapter09.html

[ix] https://nba.uth.tmc.edu/neuroscience/m/s4/chapter09.html

[x] https://nba.uth.tmc.edu/neuroscience/m/s4/chapter09.html