Science has been closing in on the Unconscious for several years now, with some elegantly designed experiments showing how people make decisions and take actions before they have the opportunity to recognize their decision consciously. The latest experiment to point in this direction was recently described in an article published in Nature magazine, Different time courses of learning-related activity in the prefrontal cortex and striatum, by Anitha Pasupathy and Earl K. Miller. The Nature abstract is dense:
To navigate our complex world, our brains have evolved a sophisticated ability to quickly learn arbitrary rules such as 'stop at red'. Studies in monkeys using a laboratory test of this capacity—conditional association learning—have revealed that frontal lobe structures (including the prefrontal cortex) as well as subcortical nuclei of the basal ganglia are involved in such learning. Neural correlates of associative learning have been observed in both brain regions, but whether or not these regions have unique functions is unclear, as they have typically been studied separately using different tasks. Here we show that during associative learning in monkeys, neural activity in these areas changes at different rates: the striatum (an input structure of the basal ganglia) showed rapid, almost bistable, changes compared with a slower trend in the prefrontal cortex that was more in accordance with slow improvements in behavioural performance. [Emphasis mine-ShrinkWrapped] also, pre-saccadic activity began progressively earlier in the striatum but not in the prefrontal cortex as learning took place. These results support the hypothesis that rewarded associations are first identified by the basal ganglia, the output of which 'trains' slower learning mechanisms in the frontal cortex.
The article was described in a release from the MIT news office, Primitive brain is 'smarter' than we think, MIT study shows. The salient points, which I highlighted above, are that in a learning situation which involves deeper, primitive brain structures and their associated higher cortical structures (the pre-frontal cortex where we believe most of our higher order cognition takes place), the lower structures learn the new "fact" well before the cortex consolidates its grasp of the facts. The MIT news release summarized thusly:
The researchers speculate that perhaps the faster learning in the basal ganglia allows us (and our primitive ancestors who lacked a prefrontal cortex) to quickly pick up important information needed for survival. The prefrontal cortex then monitors what the basal ganglia have learned. Its slower, more deliberate learning mechanisms allow it to gather a more judicious "big picture" of what is going on by taking into account more history and thereby exert executive control over behavior, Miller said.
The implication for Psychoanalysis and the structure of the mind are profound. In humans, we would correlate the basal ganglia with unconscious mental functioning; the pre-frontal cortex would be associated with conscious mental functioning. [Neurosurgeons who stimulate the pre-frontal cortex during surgery evoke conscious mental content; when they stimulate the basal ganglia, they evoke motor responses, which are noted by the patient but are without conscious content or volition.] In other words, this provides a template for the unconscious mind producing overt behavior without the involvement of the conscious mind until after the fact. This is a pretty good model for rationalization , the process whereby we explain our behaviors in acceptable ways after we have either decided to do what we want or have actually done it.
It does not require much imagination to extend this. Once we have shown the neurophysiological proof of the existence of the unconscious mind in relation to simple learning, it won't be long before we begin to show evidence for the existence of the dynamic unconscious, a fundamental tenet of Psychoanalysis and our theory of the mind.
Recent Comments