Monthly Archives: October 2012

The Epidemiology of Alzheimer’s Disease

Povova and colleagues have a paper in the journal ‘Biomedical Papers’ titled ‘Epidemiology of and Risk Factors for Alzheimer’s Disease: A Review’ which is freely available here. I found the paper interesting for the coverage of two areas

1. Prevalence and incidence rates. The authors have gathered data from numerous studies. Prevalence data will vary according to the study methodology and the characteristics of the target population. The authors refer to a 2005 Delphi Study published in the Lancet with an estimated prevalence globally of 3.9% in people over 60 years of age. However the prevalence varies considerably between countries. For the incidence of Dementia, the authors look at a number of prospective studies and express the findings in 1000 person-years. From the data it is clear that the sampling method is critical for the interpretation of the results. Although two studies may calculate the incidence of Alzheimer’s Disease in people over the age of 65 the average age of the sampled population as well as many other variables are critical in generalising these findings to other populations. Nevertheless regardless of the methodology, with figures ranging from 6.3 to 86.7 per 1000 person years it is clear that there is a significant disease burden in the sampled populations.

2. Prevention. The authors look at prevention focusing on primary, secondary and tertiary prevention strategies highlighting the role that medication, diagnosis and modifiable risk factors play in prevention.

Index: There are indices for the TAWOP site here and here Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

Does This Bonobo Have A Theory of Mind?

He who understands baboons would do more towards metaphysics than Locke” – Charles Darwin

The theory of mind is the ability to understand that you have a mental state as do others and that the mental state of others may differ from yours.  The mental state may include beliefs, feelings and other attributes of our inner world. The theory of mind has been described as a special feature of humans but there is a lot of debate about other species. For instance Dolphins and Chimpanzees are notable examples of species that are suggested to have a theory of mind although the arguments are extended to many other species.

I took the video above at Twycross Zoo and thought it rather interesting for a particular segment at 0.16-0.31. During this sequence the senior maternal Bonobo makes a number of rapid non-verbal gestures towards the infant Bonobo. These consist of gazing upwards, accentuated blinking, indicating with the head and holding and pushing with the right arm. The maternal Bonobo seems to be indicating to the infant to turn around and look in a certain direction. The direction is indicated by the maternal Bonobos gaze and when the infant Bonobo does not look in this direction, the firm holding arm of the maternal Bonobo pushes the infant to face in that direction.

This at least is my interpretation. If it is correct then it implies that the maternal Bonobo recognises the infant is not looking in the right direction. This in turn implies an inference about the visual perception of the infant. The sceptic may disagree with my interpretation and I accept that it is limited to a behavioural observation.

However if it were correct there would be two interesting points about this

1. This demonstrates the use of several non-verbal means of communication in an apparently goal directed behaviour. These gestures may have been important for the development of a theory of mind which has been so central to the success of the human race.

2. Bonobos are our second closest relatives. They are also referred to as Pygmy Chimpanzees and have branched off from the lineage of Chimpanzees. Furthermore our lineage diverged from Chimpanzees around 6 million years ago. There are vastly different estimates for this figure which tend to be modified by new estimates of genetic mutation rates and genome sequencing data. What is rather unfortunate however is that every other species that has branched off from our lineage after Chimpanzees (i.e in the past roughly 6 million years) is now extinct. This means that from an evolutionary perspective Bonobos and Chimpanzees are our nearest surviving relatives and provide us with valuable insights into our history.

In the above quote from Darwin, i’m sure he might have been equally fascinated by Bonobos which were first described in 1928 and are classed as Greater Apes.

Index: There are indices for the TAWOP site here and here Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

Building a Model of the Insular Cortex – Part 4

 

Figure showing the insular cortex (circled) in a coronal section indicated by the blue line in the inset, Modified from Original Image by John Beal PhD, Dep’t. of Cellular Biology & Anatomy, Louisiana State University Health Sciences Center Shreveport, CC-BY

This is the fourth part of a series looking at building a model of the Insular Cortex, part of the brain that is thought to play an important role in emotions and awareness. ‘In the 2009 paper ‘How Do You Feel Now? The Anterior Insula and Human Awareness‘ Craig outlines an elegant model of the Insular Cortex which integrates neurophysiological findings. In developing the current model, I thought Craig’s model of the Insular Cortex would be a useful starting point for refining the model covered in Part 1 (see Appendix)’*.

Craig has done a lot of work in sensory neurophysiology and uses this as the basis for his model. Reflecting on Craig’s review, I note that it is complex and incorporates reviews of a large number of fMRI studies investigating a vast array of psychological phenomenon. Craig notes that the Insular Cortex is activated throughout many studies investigating disparate phenomenon. Most of the studies considered involve interoception – the awareness of a person’s own body. This includes temperature, movement and body position. Noting the activation throughout such studies Craig draws the conclusion that the Insular Cortex is involved in awareness and has in his work explicitly suggested that the Insular Cortex is a location for consciousness.

Craig’s suggestion is an interesting one. I would propose that consciousness is modular – that is that our conscious experience arises from widely distributed neurophysiological activity in the brain. Furthermore different qualia of conscious experience are physiologically grounded in correlated neuroanatomical regions. For visual consciousness there is the visual cortex and associated areas, for auditory consciousness there is the auditory cortex and so on. Craig’s proposal here is what I would refer to as a top level concept. In a top down hierarchy of concepts – the key concepts that give an overview of the subject area and inform that structure would be at the top of the structure. In building a model it is useful to start off with this approach. The top level concept therefore is that the Anterior Insular Cortex is a key brain area for ‘awareness’ and ‘consciousness’ as it is activated in numerous studies investigating various phenomenon. Other aspects of Craig’s review would then allow the other aspects of this model to be clarified with neurophysiological correlates.

In considering Craig’s model however it is useful to explore alternatives as this helps to shape the model using the theme of the Hegelian Dialectical. In the first instance the suggestion that the Insular Cortex is activated in many fMRI studies does not necessarily imply that it is an important region for awareness. This activation could be an artefact of fMRI methodology. In this regards the authors of one review have suggested that the Insular Cortex plays an important role in processing vestibular inputs. For example this includes the experience of self-motion. In fMRI studies, it has frequently been noted that research participants undergoing fMRI will experience vertigo. Furthermore there is evidence to suggest that the magnetic field inside the MRI scanner stimulates the vestibular apparatus.

Therefore one alternative hypothesis is that the Insular Cortex is frequently activated in fMRI studies as an artefact due to magnetic field stimulation of the human vestibular apparatus with subsequent processing of the sensory input into the Insular Cortex. Although this is unlikely to be the case, consideration of this alternative hypothesis will help to refine the original hypothesis and hopefully make it more robust.

Insular Cortex Resources on this Site

What does the Insular Cortex Do Again?

Insular Cortex Infarction in Acute Middle Cerebral Artery Territory Stroke

The Insular Cortex and Neuropsychiatric Disorders

Developing a Model of the Insular Cortex and Emotional Regulation Part 1 Developing a Model of the Insular Cortex: A Recap

The Relationship of Blood Pressure to Subcortical Lesions

Pathobiology of Visceral Pain

Interoception and the Insular Cortex

A Case of Neurogenic T-Wave Inversion

Video Presentations on a Model of the Insular Cortex

MR Visualisations of the Insula

The Subjective Experience of Pain

How Do You Feel? Interoception: The Sense of the Physiological Condition of the Body

How Do You Feel – Now? The Anterior Insula and Human Awareness

Role of the Insular Cortex in the Modulation of Pain

The Insular Cortex and Frontotemporal Dementia

A Case of Infarct Connecting the Insular Cortex and the Heart

The Insular Cortex: Part of the Brain that Connects Smell and Taste?

Stuttered Swallowing and the Insular Cortex

YouTubing the Insular Cortex (Brodmann Areas 13, 14 and 52)

New Version of Video on Insular Cortex Uploaded

*Text taken from Part 3.

Index: There are indices for the TAWOP site here and here Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.