Julia Krestow, BSc, MSc
Scientists working on the cutting edge of neuroscience met in Toronto, March 20-24, at the 10th Annual Rotman Research Institute Conference. Over 800 participants from 33 countries were attracted by this year's theme--the Frontal Lobes--making it the largest scientific conference ever held on frontal lobe research.
Only during the last decade or so, has knowledge emerged demonstrating the frontal lobe's critical role in uniquely human attributes such as, sense of humor, emotion, planning and organizing for the future. Even moral judgement and decision-making is beginning to be understood, with some studies implicating damage to the frontal lobes as the cause of criminal behaviour. The media was out in full force, with several articles in the daily papers, interviews on the CBC and daily briefings on the Discovery channel's website, demonstrating the enormous public interest in the prefrontal cortex (PFC).
Dr. Robert Knight of the University of California, Berkley, began his closing remarks for the conference by briefly reviewing the roots of frontal lobe research (which appear to go back to the 1880s), before going on to concentrate on the future implications of research presented throughout the weeklong conference.
The last decade has ascribed personality changes to damage in the orbital frontal cortex. According to Dr. Knight, this "is a critical area of research and a very neglected one". Bilateral orbital frontal damage typically results from trauma, either head injury or infarctions, although sometimes it is the result of meningiomas. These patients are generally tagged as having acquired a sociopathic personality disorder. Dr. Knight asserts, however, that "these people don't go out and become multiple murderers; most of their problems are reflexive bad behaviour and in fact they know their behaviour is wrong and they are not happy about it".
He further explained that the speed with which these patients make their mistakes, an aspect of reflexive behaviour, is too fast for the autonomic nervous system to monitor. The very prominent disinhibition of these patient's PFC, when presented with novel stimuli, necessitates a scientific model (to explain behaviour) that must incorporate both the peripheral autonomic problem, which may be decreased, and the central hyperresponsivity. The current speculation is that due to a disconnection patients are prevented from integrating these two critical functions.
Integrative neuroscience is dependent on a solid understanding of neuroanatomy. Dr. Knight even suggested that "imaging has become the rage because it's a neuroanatomical method". It is precisely this knowledge that allows for the neuroanatomical tracing of networks to the remotely-exibhited effects of lesions elsewhere in the brain. For example, studies have shown that an infarction of the posterior cerebral artery may result in a hippocampal infarction and ultimately in unilateral deterioration of mammilary bodies. Imaging techniques have advanced to the point where Magnetic Resonance Imaging scans are capable of mapping white matter tracts or 'network productivity highways'. Experiments have already been planned to look one step beyond anatomy into activation networks, wherein activation in one area will initiate activation in other areas according to a well-defined pathway. Dr. Knight believes it "will be THE technique probably in neuropsychological research and in functional imaging".
A large portion of the conference centered on sensory research where subjects are presented with stimuli (auditory, somatosensory, visual) and asked to respond to a chosen target. Normally, the activation of prefrontal cortex hippocampus is acutely sensitive to habituation with activation fading away rapidly. Studies using EEG, lesion and intracranial recording data (electrode inserts into brain) have suggested that the trigger for stimuli detection is the PFC, which then engages the temporal parietal cortex, and hippocampus. Recently there have been reports in which EEG temporal data converges with MRI spatial information. The significance of such advances is described by Dr. Knight as the "Rosetta stone,"which culminates in "real time spatial temporal information in humans".
Dr. Knight's own research supports a model for top-down control by the PFC in the visual system. By looking at responses to standard and target stimuli in patients with frontal lobe lesions he reports a "tendency for all patients, no matter what their disorder is, [to] get the sensory information in and transfer rapidly to other hemisphere [to] solve the task with the intact [undamaged] frontal lobe".
This research supports one of the key take home messages from the conference: a general principle of prefrontal function is that it controls the activity of the PFC in distributed neural networks in posterior brain regions, or in simple terms, the ability of the PFC to distribute information to the appropriate areas of the brain for further processing.
Dr. Knight's firm belief is that one of the "unique features of the prefrontal cortex is to allow you to go rapidly through time transitions back and forth". Perhaps it is this combination of switching, inhibition (of the present), and excitation (facilitating neurorepresentations of the past and future) that defines consciousness.
To understand consciousness is the ongoing challenge. The anatomy of millions of neurons and circuits of neurons is the hardware. Consciousness, created by the integration of emotion and thought, both complex processes in their own right, is the software. Understanding how one creates the other is the current quest of neuroscientists. Robert Knight points out that this will be particularly challenging, but he is confident that, though daunting, the goal is achievable.
