Patient H.M.

Today’s blog post is about one of the most studied individuals in psychology and neuroscience. By studying him, scientists were able to massively expand their knowledge of how to human brain is structured, and how different abilities (or “functions”) are located in different cortical areas.
H.M. was born in 1928, and was 10 when he first started having epileptic seizures. These were extremely debilitating, and although several medications were tested, none had any affect. When H.M. was 27, a pioneering neuroscientist called William Scoville worked out where the seizures in H.M.’s brain were coming from, and decided that the best way to stop them was to operate, and cut out the parts of the brain that was responsible.
In terms of removing his seizures, this surgery was largely successful. However it came at a cost: H.M. could no longer form new long term memories, nor remember anything from X years before his operation. The image below is a scan taken of H.M.’s brain, and shows the lesions made during surgery, and how this differs from a normal brain scan.
memory-hm-anatomy2
As you can see from this image, H.M. was left with extensive damage to the central parts of his brain – this area is known as the medial temporal lobe. By analysing the brain damage, neuroscientists were able to make inferences about where certain brain functions are located. As H.M.’s memory was impaired, but other cognitive functions such as language were not, the medial temporal lobe was identified as being important in the formation of long term memories.
Perhaps unsurprisingly, things aren’t as simple as this. H.M.’s long term memory was affected, so severely that he was unable to remember things that happened a few minutes ago. However his short term memory was intact, with a normal digit span (a string of numbers that you can keep in your mind at once) of 7 +/- 2. Therefore, the structures damaged can’t be involved in short term memory.
There are also distinctions that can be made within long term memory. This can be divided into 3 different types of memory: semantic, which is general knowledge about the world; episodic, which are memories about ourselves and our lives; and procedural, which are learned physical movements e.g. riding a bike. Only H.M.’s episodic and semantic memory were damaged, which shows that our procedural memory must be located elsewhere. Other brain areas such as the cerebellum have been identified as involved in this. Not only was his procedural memory intact, he could also improve it by practicing new movements over time. The image below shows a mirror drawing task, where participants have to trace an image by only looking at its reflection in a mirror.
starmirror
H.M.’s performance improved each time he did this task, even though he had no recollection of ever doing the task before! This illustrates nicely the different between the automatic, learned ‘procedural’ memories, and the episodic memories about previous experiences.
One last question remains – why did H.M. lose his episodic memories from the years before the operation, but not ones from when he was much younger? There are several theories for this, with one being that older memories are ‘consolidated’ into the rest of the cortex – only newer memories remain in medial temporal structures such as the hippocampus. Therefore, when this area of brain was destroyed, so were the newer long term memories.
When H.M. died in 2008 aged 82, scientists were able to reveal his real name – Henry Molaison. He made a massive contribution to the field of neuroscience, and is thought to have been one of the most tested patients in medical history.
For those interested in reading more about H.M., I would recommend this article, written while he was still alive: Corkin, S. (2002). What’s new with the amnesic patient HM?. Nature Reviews Neuroscience3(2), 153-160.
And finally, I’ll leave you with a quote from H.M. himself, when he was asked “Are you happy?”
“Yes. Well the way I figure it is, what they find out about me helps them to help other people. And that’s more important.”

Epilepsy

Epilepsy is a neurological condition characterised by repeated seizures. Seizures are caused by electrical activity in the brain, although may appear differently from person to person (not all seizures involve convulsions, despite what you might think).

As with many conditions there is not a single cause that can be identified as a precursor to epilepsy. Genetics (a mutation in the KCNC1 gene has recently been identified as a cause of a progressive inherited form of epilepsy – Muona et al 2015), brain tumours, or head injuries, and the cause of many patients’ epilepsy remains unknown. Several studies have shown that you are more likely to develop epilepsy after a head injury e.g. Christensen et al (2009) found that people were 2% more likely to develop epilepsy after a mild head injury. This rose to 7% more likely following a severe head injury, with risk also increasing slightly with age.

The image below is taken from the EFEPA and shows what to do if someone is having a seizure:

first-aid-for-seizures3_page_2

As mentioned earlier there are different types of epileptic seizures which depends on which part of the brain they originate in. Seizures can be classified by how much of the brain is affected: partial/focal seizures (when only a small part of the brain is affected) or generalised (if most of the brain, or all of it, it affected).

Focal seizures can also originate in different parts of the brain, with the temporal lobe being the most comment (epilepsy.com). The temporal lobe is the part of the brain above your ear, and is responsible for processing hearing, and our memories (this is simplified – it does a bit more than this!). Therefore, one of the common features of temporal lobe epilepsy is memory disturbances (Ko et al, 2013). The famous patient H.M.’s amnesia was caused by an operation to remove the source of his severe temporal epilepsy – this was carried out in the 50s before brain functions were accurately known and too much of the medial temporal lobe was taken away. This destroyed part of the hippocampus, the structure in the brain responsible for memory processing. Due to the nature of his amnesia, he was probably one of the most studied individuals ever in psychology. See this post for more on H.M. and memory research. Operations are carried out to remove part of the temporal lobe in patients now with much better outcomes!

The second most common is frontal lobe epilepsy, where seizures originate in the front part of the brain. They often occur during sleep, and can affect the motor areas of the brain, leading to problems with motor skills (e.g. Beleza & Pinho, 2011). If patients are not eligible for surgery to remove the specific part of the brain responsible for the seizures, anti-convulsive medication and electrical brain stimulation can be helpful in reducing symptoms (Kellinghaus & Luders, 2004).

 

 

 

Autism

Hi everyone, I hope you liked my last post on how children develop a theory of mind – this post follows on, and talks about children with autism (if you haven’t read that post, find it here https://freudforthought.wordpress.com/2015/08/06/theory-of-mind/).

Autism is a neurodevelopmental disorder, which has a prevalence of 60 per 10,000 children under 8 in the UK (Baird et al, 2000). Characteristics of autism include impairments in social interactions, communication, and imaginative behaviours. Also, individuals with autism tend to like to stick to routine, and can become distressed if their routine changes. However, autism is a spectrum, and sufferers can have a range from very mild, to severe impairments. For example, the disorder formerly known as Asperger’s Syndrome had all the characteristics of autism, but without the language difficulties (however this is now no longer recognised as a separate disorder).

Criteria for social impairments include lack of eye contact during interactions, and the lack of voluntarily sharing interests and enjoyment with others. Communication impairments include a delay of language development, and a lack of varied pretend play. Finally, examples of repetitive behaviour include sticking to rituals, and a preoccupation with the parts of objects. As mentioned in my last post, some of these behaviours can be explained by deficits in a theory of mind, which is a theory proposed by Baron-Cohen et al.

As well as the traditional theory of mind tasks, they also carried out more advanced experiments, called ‘reading the eyes’ tasks. In these, adults with autism were shown pictures of people’s eyes, and had to work out the emotion the eyes were showing. They found that autistic participants made more errors than controls without the disorder. However, it is worth noting that this task is challenging to normally developed adults – see how you get on from the picture below!

eyes

One other interesting thing about autism is that it is more common in males than females, with a 3:1 ratio. Baron-Cohen (2003) therefore outlined his theory that autism is an extreme form of the male brain. This theory states that everyone has either a male or female brain, regardless of their actual gender, with the male brain being better at systemising, and the female brain better at empathising. As autistic individuals can struggle showing empathy, and are generally interesting in how things work, he hypothesised that autism reflects the male brain. Despite the terms ‘male’ and ‘female’, he found that about 17% of men had a ‘female’ brain, with the same percentage of women having a ‘male’ brain. Many people also have a balanced brain, showing aspects of both.

I kind of get why he came to this conclusion, but I think that this theory is very oversimplified, and that there is actually no need for the terms ‘male’ or ‘female’ at all – especially as people can have aspects of both, and that the brain type has nothing to do with gender! Might be one theory to take with a pinch of salt…

But what do you think? Let me know in the comments and thanks for reading!

Visual Extinction

Visual Extinction is a condition caused by damage to the parietal lobe, and is similar, although distinct from Visual Neglect.

It is characterised by the ability to see stimuli in the opposite visual field to the brain damage, but only when there is no competition from other stimuli in the visual field on the same side as the brain damage. If there are stimuli in both visual fields then only the one which is projected to the intact side of the brain will be seen.

It is diagnosed using confrontation testing:
– the experimenter wiggles their left/right fingers or both in the air while sitting opposite the patient
– patient can detect each finger when they are presented separately
– however, if both are presented then they can only detect the finger on the left (assuming the right parietal lobe is damaged)

The video below shows a variation of this technique:

However, there are some circumstances in which extinction can be reduced.

Riddoch (2003) presented patients with pairs of objects, which were correctly or incorrectly presented for action. For example, a corkscrew pointing towards the cork in a wine bottle (correct), or at the bottom of the bottle (incorrect).
The results showed that they were better at reporting both items when they were correctly presented for action. When one item was extinguished, they were more likely to report the active item, even if it is in the impaired visual field.
Therefore, which object they reported was influenced by the interaction between them.
This finding was important as it suggests that extinction occurs quite late, in higher-order visual areas and there is some unconscious processing of extinguished items.

Like Neglect, extinction can also occur in motor actions, not just vision.
For example, several case studies have shown that patients can use both arms equally well separately, but become much worse at using their bad arm when doing so at the same time as the good arm.

Hope you enjoyed this post – don’t forget to check back soon for more!