22 March 2007

Neural Rhythms, Moral Minds

My two favourite mind/brain blogs are Developing Intelligence and Neurophilosophy. Chris Chatham has another fascinating post on the theme of neural oscillations--Alpha Oscillations and Consciousness.
More recent work provides a detailed view of how alpha-band oscillations may contribute to cognition. Palva & Palva review evidence that large amplitude alpha oscillations may actually perform a different function than lower-amplitude oscillations in the same frequency band. In a visual search task, for example, alpha-band oscillations are dampened in active visual cortex and enhanced in inactive regions of visual cortex, but both small and large alpha band activity prior to the onset of the visual stimulus was correlated with better subsequent performance! One could conclude that these alpha-band oscillations reflect preparation for the task by generally "calming the waters" in cortex (either through alpha phase locking or alpha amplitude suppression) so that activity due to the upcoming visual stimulus can be readily detected

...Palva & Palva previously found cross-frequency phase coupling in every frequency band from delta to gamma, and that this coupling was stronger during mental calculation as well as high working memory load - in particular, the strength of alpha-gamma coupling. The authors argue that a variety of behaviors are synchronized at alpha rhythms, including human serial recognition/categorization speed, the timing of illusory motion reversals in the wagon wheel illusion, discrimination of odors by rats, and phasic muscular activity (including "alpha tremor").

MC presents a recent study from Antonio Damasio and Marc Hauser (author of Moral Minds) about the ventromedial prefrontal cortex (VMPC) and its likely role in moral judgment:
In the current study, the intelligence and logical reasoning of the six patients with VMPC damage was unaffected, and they all had full knowledge of social norms. However, they all displayed impaired autonomic responses to emotionally-charged images, and, in line with the previous findings, had a significantly diminished sense of empathy, embarrassment and guilt.

Thus, the findings confirm the notion that there are at least two neural systems involved in making moral decisions: one in which emotions are involved, and one which performs a cost-benefit analysis. The former appears to be disrupted in the six patients with VMPC cortex, while the latter is intact. It is believed that the emotion-based system for making moral decisions evolved first, perhaps in a situation where small numbers of people lived in kin groups. Damasio says, “A nice way to think about it is that we have this emotional system built in, and over the years culture has worked on it to make it even better”.

Here is a link to a podcast interview with Marc Hauser from Neurophilosophy discussing his recent book Moral Minds You may observe in the podcast interview that the blank slate hypothesis dies very hard in an Idiocracy, but if for no reason other than general apathy, its days are numbered.

The two above articles help to clarify important research findings for important areas of brain and consciousness research. Both neuroblogs above keep close track of neuroscience research, and are well worth following on a regular basis.

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