Are all functions highly localised?

We have explored the concept that functions may be localised and have looked at examples for some of the sensory functions that the brain performs. Of course, we don’t just have a brain to take information in but also to allow us to respond to that information appropriately. For example, if we hear a familiar voice in the distance we may want to move towards it to meet that friend. We can find regions of the brain responsible for coordinating our movement that are the primary and association motor cortices that we can think of as being equivalents to the sensory regions we met earlier this week.

However, there is more to human behaviour than simply “sensory information in, appropriate movement response out”. Earlier this week, we met the idea that pain involves more than just simple sensory information and in my example above, what wasn’t mentioned is why we might want to move towards the recognised voice – most likely because we would be pleased and happy to see and talk with that friend. This, of course, generates some obvious questions:

What does it mean that we are “pleased” or “happy”?

and

What does the brain have to do with this?

Feelings of pleasure or happiness can be thought of as being examples of our emotions. From your own experience you will know that emotions don’t have to be positive like happiness, but can be negative, such as sadness or being angry or disgusted. We also now know that emotions have their origins in the brain and, biologically, are underpinned by the principles of neuronal cell function that we have met in previous weeks. So, a reasonable question to ask might then be:

Where in the brain do emotions originate?

In everyday language we could be asking whether somewhere in your brain there is a region responsible for happiness or outrage. In fact, all of the evidence suggests that emotions are highly complex processes requiring the integration of lots of information and as such there is no single region but a collection of regions which all contribute to producing how you might feel and behave emotionally. Furthermore, our emotional state may also be integrated with sensory information, as in the example above. Perhaps something you might have experienced yourself is how emotionally powerful listening to music can be – which is the subject of the next step. Research has begun to explore how different regions are connected together and have generated some amazingly beautiful images of the maps of connections. You might want to search for “connectome” to see some for yourself.

The functional consequence of having this more dispersed organisation rather than small regions with discrete functions has both good and bad aspects. On the “good” side, it means that damage to a small area of brain is unlikely to affect the individual emotionally as profoundly as damage to the primary visual cortex would affect vision. However, on the downside, this makes it more difficult to research the neuroscience of emotions under both normal and disrupted circumstances, for example in the case of depression. As a consequence our ability to find effective therapeutic options for conditions where emotions are disrupted has been limited.

In week two, you investigated how antidepressant drugs could affect aspects of the neurotransmission process for particular neurotransmitters involved in processing emotion-related information. Unfortunately, whilst this could result in improvement of symptoms, the neurotransmitters and pathways that are targeted are fairly widespread in the nervous system and as a consequence the drugs have multiple unwanted effects.