Brains that go bump in the night.
Brain science has come a long way in the last 200 years. We look back at the early efforts of the phrenologists to map personality, behaviour and mental abilities onto specific organs of the brain with amusement. But that is only because their methodology was so woefully inadequate. These brain organs were supposed to affect the contours of the skull and a skilled phrenologist would take measurements of the skull and use his clinical judgement to interpret them in order to draw conclusions about a person’s character or mental capacities.
The early phrenologists relied upon post mortem studies of the brains and skulls of criminals and the insane. They were looking for things like the theft organ or the murder organ. Later the focus shifted to more generalized concepts, seeking organs for greed, jealousy, benevolence or self esteem.
Modern brain imaging techniques enable today’s neuroscientists to see the brain in action in living subjects. They have given us a detailed anatomical map of the brain and have been able to succesfully map particular functions to specific areas of the brain. Their results provide a more reliable guide to the workings of the human brain than the phrenologists ever could.
It is important to remember that, despite having access to so much more accurate data about the brain than the phrenologists ever had, we have not moved on that far in our ability to interpret the data. We are still ruled by the belief that specific parts of the brain are responsible for different types of behaviour. Sometimes this belief is well founded. Language areas, motor areas, the visual cortex; all have been reliably mapped.
Just as every sin contains the seed of its own salvation, so every virtue contains the seed of its own corruption. Success in mapping so many functions onto specific areas of the brain has reinforced the belief that the determinants of all human behaviour can be located within specified areas of the brain. This takes us back beyond phrenology to Descartes and the dichotomy between body and soul. Just like phrenology, the Cartesian dualism of body and soul is another idea that has persisted beyond its time. Only now it refers to the biological determinism of the brain ruling the body; rather than the spirit being superior to the body.
Descartes also knew a thing or two that apear to have eluded modern reductionists in science. He did not regard the brain as the arbiter of all human behaviour, bodily passions could overrule the brain and lead us into irrational behaviour as well. This particular model of human behaviour as a struggle between higher mental function and lower animal instincts is no longer given scientific credence, though it persists in theology and some forms of Freudian psychiatry. But the principle that biofeedback mechanisms within ourselves as well as external pressures can act to modify behaviour is a necessary corrective to the belief that biological determinism begins and ends in our genes.
If we are a product of our brains, our brains are a product of our DNA. There is a multi-million dollar research programme to discover the genes that cause autism. Strictly speaking, the genes do not cause autism. Researchers are looking for mutations in the genes that code for the proteins that build the parts of the brain that control the behaviours that are supposed to be impaired in autistic people. But in the popular consciousness we have already had attempts to discover the Gay gene, the gene for aggression, etc. Media coverage of genes and autism will inevitably reinforce the popular belief that genes code for behaviour.
Autism Under the Gyruscope
Never mind. The scientists know what they are looking for, don’t they? Well sort of. At one time scientists believed they had identified a part of the brain that plays a crucial role in face recognition. Attending to and remembering faces is a problem for many autistics. It is also a problem for me. So I have been following this research with some interest.
In 2001 Karen Pierce et al. published a paper, Face processing occurs outside the fusiform `face area’ in autism: evidence from functional MRI, that showed that unlike non-autistic controls,
Overall results revealed either abnormally weak or no activation in FG [fusiform gyrus] in autistic patients, as well as significantly reduced activation in the inferior occipital gyrus, superior temporal sulcus and amygdala.
Again, quoting from the abstract,
Such a pattern of individual-specific, scattered activation seen in autistic patients in contrast to the highly consistent FG activation seen in normals, suggests that experiential factors do indeed play a role in the normal development of the FFA. [fusiform facial area]
The argument seems to be that autistic children spend less time looking at faces than normal children. So their FFA is impaired from under use. At the time this made perfect sense to me and encouraged me in my practise of teaching eye contact and facial recognition to my autistic pupils. But according to Pierce the autistic adults in her study where just as good at the task as the control group. The abnormality was in the brain areas they used to perform the task. These adults had obviously trained themselves in facial processing. So why hadn’t their FFA kicked in when they did take an interest in faces?
This suggests that autistic brains have impaired or different wiring. But it does not explain why. The picture was further complicated when Geraldine Dawson reported that children took time to develop their fusiform gyrus but it was normally fully functional by age 12. Perhaps there is a window of opportunity when the FFA can be activated but once this has passed other pathways have to be utilized.
She showed pictures of cars and faces to 11 autistic adolescents and adults and to 10 age matched controls. In all of them the temporal inferior gyrus reacted normally, activating in response to the cars. It also activated in response to the faces in the autistic subjects. There was one anomaly. Autistic subjects did use their fusiform gyrus when looking at pictures of their mothers. I wrote at the time,
This suggests to me that (contrary to the popular belief that autistic aloofness arises from the fact that their brains are differently wired) intense emotional experiences may help to shape brain function. ACs have brains that can work in exactly the same way as their NT counterparts. The fact that they do not respond to everybody in the same way just goes to show that their brains are just far more discriminating in the range of stimuli and experience that shape their response. As ever with autism, the actual mechanisms are far more subtle than we first imagined.
I had no idea what I was talking about! I see echoes of Victor and Dr Itard in those “intense emotional experiences.” there are also dubious echoes of holding therapy, a misguided and dangerous attempt to force an emotional bond with the mother where none was presumed to exist. The truth is I could not explain the anomaly and was rather clumsily using it to make the point that we are a long way from fully understanding autism.
Rectifying the Anomaly
The one good thing about science is that scientists love an anomaly. If something blows a hole in the current theory, a good scientist will find it interesting and follow it up. As it happens I was not too wide of the mark with my guess that,
their brains are just far more discriminating in the range of stimuli and experience that shape their response.
What if the fusiform gyrus is not an area for processing faces? What if everybody’s brains are more discriminating than we imagined? In this paper the fusiform gyrus and the inferior gyrus are both implicated in an expert object recognition pathway.
Brain imaging studies suggest that expert object recognition is a distinct visual skill, implemented by a dedicated anatomic pathway. Like all visual pathways, the expert recognition pathway begins with the early visual system (retina, LGN/SC, striate cortex). It is defined, however, by subsequent diffuse activation in the lateral occipital cortex (LOC), and sharp foci of activation in the fusiform gyrus and right inferior frontal gyrus. This pathway recognizes familiar objects from familiar viewpoints under familiar illumination. Significantly, it identifies objects at both the categorical and instance (subcategorical) levels, and these processes cannot be disassociated. This paper presents a four-stage functional model of the expert object recognition pathway, where each stage models one area of anatomic activation. It implements this model in an end-to-end computer vision system, and tests it on real images to provide feedback for the cognitive science and computer vision communities.
Expert object recognition? Perhaps the Fusiform Gyrus reacts to faces because most of us have an interest in faces and become quite expert at recognizing them. What if we became expert in something else. Would that light up the fusiform gyrus? Isabel Gauthier et al tested this by creating a set of novel objects called greebles and training volunteers to become greeble experts.
The strongest interpretation suggested by our results together with previous work is that the face-selective area in the middle fusiform gyrus may be most appropriately described as a general substrate for subordinate-level discrimination that can be fine-tuned by experience with any object category.
One of Gauthier’s collaborators, Michael Tarr, has reported on similar research with extant experts and, just as with the Greebles, the fusiform gyrus is involved
Several of our findings speak directly to the question “Are faces special?” First, Greeble experts, but not Greeble novices, show behavioral effects – notably configural processing – that are often taken as markers for specialized face processing (Gauthier & Tarr, 1997; Gauthier et al., 1998). Second, Greeble experts, but not Greeble novices, show category-selectivity for Greebles in the right fusiform gyrus (Gauthier et al., 1999). Similarly, bird experts show category-selectivity for birds, but not cars, in the right fusiform, while car experts show category-selectivity for cars, but not birds (Gauthier et al., 2000). Reinforcing the generality of this result, chess experts, but not chess novices, likewise show category-selectivity in right fusiform for valid, but not invalid, chess game boards (Righi & Tarr, 2004). Third, across Greeble expertise training, subjects show a significant positive correlation between a behavioral measure of holistic processing (sensitivity to the presence of the correct parts for that object) and neural activity in the right fusiform (Gauthier & Tarr, 2002). Similarly, bird and car experts show a significant correlation between their relative expertise measured behaviorally (birds minus cars) and neural activity in the right fusiform (Gauthier et al., 2000). Behaviorally measured chess playing ability also shows a significant correlation with right fusiform response (Righi & Tarr, 2004). Fourth, the N170 potential (as measured by event-related potentials) shows face-like modulation in Greeble (Rossion et al., 2000), bird and dog experts (Tanaka & Curran, 2001), but only for a given expert’s domain of expertise.
So is the anomaly solved? Autistic children become experts on significant adults like mothers and thus arouse the fusiform gyrus when they see a picture of Mum. That still leaves open the question of why autistic children are not naturally interested in faces or social interaction to the same extent as their peers. Will the neuroscientists now go looking for the brain area that motivates us to become people experts? And when they find it how will they know it is the people area and not a different category of area that just motivates us to become experts?
It would be really nice if all those parents that yearn for some acknowledgement of affection from their autistic children could be shown an fMRI scan of their child’s fusiform gyrus lighting up when they walk in the room.