[Editor’s note] Useful links:
- Original article by Sumaiya Shaikh, published July 18, 2017
- Rebuttal to the original by Shruti Muralidhar – below
- Sumaiya Shaikh responds to the rebuttal, published July 19, 2017
This is in response to Sumaiya Shaikh’s article in The Wire titled ‘The Cognitive Neuroscience of a Lynching’. She has attempted to explain the human behaviour seen in acts of extreme violence, such as lynching. As a trained and practising neuroscientist who works in the field of learning and memory, I find that a lot of the neuroscience in her article is unsubstantiated, outdated or plainly incorrect. Following are some chosen paragraphs from her write-up, accompanied by my comments.
Sumaiya Shaikh: In the absence of information exchange from the hand and the brain, a new altered communication pattern harbours reduced neuronal synaptic connections or ‘empty space’ in the brain corresponding to the injured part.
Shruti Muralidhar: If I understand Shaikh’s analogy correctly, she is using the term ‘empty space’ to denote reduced or lack of normal synaptic connections. But the reference to ‘empty space’ is misleading.
Years of studies in anatomy, morphology and physiology have clearly shown that neurons, glia, epithelial cells, immune cells and blood vessels sit packed very tightly in the confined space of a mammalian skull. A recent study by Jeff William Lichtman, of Harvard University, in high-definition, high-throughput electron microscopy shows that, in fact, there is no ‘empty space’ in the brain.
SS: An attempt to rationalise the racial attack by the victim and its incomprehension can lead to a long term memory consolidation that links previous experiences of the people in the mobs with the current situation.
SM: In this excerpt, Shaikh appears to have misunderstood and misused the term ‘long term memory consolidation’.
Long term memory consolidation is a slow and multi-step process that occurs over hours, days or even weeks. It involves the strengthening of connections between neurons or groups of neurons in the brain, with the final goal of retaining a particular memory. It involves changes at many different levels: neurons start or stop making specific proteins; they grow or retract protrusions known as spines to contact neighbouring neurons; they change the profile of receptors on their surfaces and sometimes even increase or decrease the amount of neurotransmitters they release.
Using the term ‘long term memory consolidation’ simply in lieu of ‘memory’ or ‘remembering’ is inappropriate and wrong – especially in the context mentioned by the author.
SS: Neuroscientists have also shown that mirror neurons, using the same mechanism that activates empathetic response for others’ pain, mimic the goal-oriented movements by activating the premotor cortex. The amygdala, a part of the brain related to empathy, is thought to be involved with the premotor cortex in initiating a mob response that requires physical action.
Mirror neurons were first discovered while recording from neurons in monkeys. Researchers found that certain groups of neurons in the cortex showed an increase in activity in two separate cases. One, when the monkey performed a certain action, and two, when the monkey observed the action being performed. This led to their moniker because these neurons ‘mirror’ activity, as if the primate itself was performing the action.
To begin with, mirror neuron research in neuroscience has been mired in controversy since 2009. A good part of this controversy relates to extending the idea of a ‘mirror neuron system’ to explain human behaviour. Direct observations of mirror-neuron activity have been performed in monkeys and higher primates – but not in humans. Non-invasive techniques such as positron emission tomography (PET) or functional magnetic resonance imaging (fMRI) applied to the human brain have only yielded information about changes in blood-flow in gross regions of the brain. However, there has been no direct evidence of changes in specific neuronal activity.
To use such an example to explain mob mentality – without explaining the caveats behind the research – is unfair to the readers and goes against good science communication practices.
Secondly, there are no known physical pathways that originate in the amygdala and terminate in the premotor cortex. This is factually incorrect.
The motor cortex is that part of the brain where physical actions – such as limb movement in response to stimuli – are planned and executed. There are many well-studied accessory areas such as the premotor cortex, the supplementary motor cortex and the secondary motor cortex. All of them play vital roles in integrating sensory information from across the brain to generate the movement response. To claim that part X of the brain ‘initiates’ a physical action, we first need to verify whether neurons from X send projections – physically – to any of the motor cortices.
There is no anatomical or morphological evidence that the amygdala sends such a physical projection to any of the brain areas involved in motor behaviour.
SS: Cognitive processes in the elimination of the self
The write-up under this sub-headline is terribly misleading. Shaikh does not explain anything related to cognitive processes in the elimination of the self. Instead, she abandons her original ‘autotomy’ analogy and starts using an ‘immune system’ analogy. Neither of these have anything to do with neuroscience, cognitive neuroscience nor any processes related to the self.
Shruti Muralidhar is a neuroscientist in Cambridge, Massachusetts.