09 Jan Brain Location Of Attention And Focusing Ability Identified
MedicalResearch.com Interview with:
Julio C. Martinez-Trujillo, MD, PhD
Canada Research Chair in Neuroscience
Associate Professor, Department of Physiology McGill University
Montreal, Quebec, Canada
Medical Research: What is the background for this study? What are the main findings?
Dr. Martinez-Trujillo: Humans and other primates have an extraordinary ability to voluntarily and efficiently focus attention on important information while ignoring distraction. For decades it has been hypothesized that this ability relies on the evolutionary expansion of the lateral prefrontal cortex, a part of the brain located in the lateral convexity of the frontal lobe, that reaches its highest level of complexity in primates. Several studies have demonstrated that the activity of single neurons in the lateral prefrontal cortex of behaving primates is strongly modulated by allocating attention to different objects or locations. However, one fundamental outstanding question in this field of research is whether assemblies of simultaneously active lateral prefrontal cortex neurons (neuronal assembly) can generate sufficient information to implement the cognitive operation of attention. This is not trivial since when multiple neurons are simultaneously active the amount of information they generate depends on processes such as correlated noise and trial-to-trial response variability, which can substantially impair the information carried by a neuronal population.
In order to investigate this issue we recorded the activity of hundreds of lateral prefrontal neurons in non-human primates while they allocated attention to one of several objects across the visual field. We input the recorded signals into a machine-learning algorithm running on a personal computer that mimicked the computations performed by a brain network of interconnected neurons. We tested the hypothesis that the computer will reliably signal where the subjects allocated attention on a computer display. Indeed, the machine could predict with 100 milliseconds resolution where the subjects directed attention on the display. This prediction was made well in advance the subjects executed any action towards the attended object. Thus, assemblies of prefrontal neurons can reliably signal the allocation of attention across the visual field within realistic timeframes.
Medical Research: What should clinicians and patients take away from your report?
Dr. Martinez-Trujillo: We found that subtly manipulating the correlated activity and therefore the functional interactions between the recorded neurons significantly altered the performance of the machine at focusing attention. This demonstrates that interactions between neurons in the lateral prefrontal cortex play a fundamental role in the amount of information neuronal assemblies can encode. These results are highly relevant across several disciplines including Neuroscience, Psychiatry, and Neurology. They demonstrate that the primate lateral prefrontal cortex plays a fundamental role in implementing the cognitive function of attention. They further indicate that inability to focus attention, as seen in patients with ADHD, Autism and Schizophrenia, may originate from subtle changes in the microstructure of the lateral prefrontal network that modulate the way individual neurons interact with one another. Additionally, because the machine could robustly decode the allocation of attention over multiple weeks, these findings open new venues for the emerging field of cognitive neuroprosthetics. It shows that brain signals can be extracted from the lateral prefrontal cortex for a brain machine interface to “read out” a subject’s intentions well in advance of a motor action toward a desired goal, e.g., reaching grasping or moving toward an object. This can potentially improve the performance of existing neuroprosthetics using brain signals to drive mechanical devices that aid patients with paralysis.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Martinez-Trujillo: We need to find a way to map the microcircuitry of the lateral prefrontal cortex in primates. To investigate whether changes in connectivity between neurons produce symptoms similar to the ones seeing in patients with disorders of attention. There are new available tools such as mutielectrode recordings, Optogenetics, and local and systemic drug delivery that will be of great value. If we can produce a model of these disorders by manipulating the activity of neurons in the lateral prefrontal cortex, we can proceed to generate interventions to rescue the disease phenotypes. The latter means we may be able to help patients with disorders of attention to better concentrate and improve their quality of life. Another important step is to find out whether small changes in lateral prefrontal cortex circuitry can originate during development. This will likely require the use of transgenic primates, something that the Japanese are taking very seriously. We should remember that only Autism is affecting 1 in 58 children, and we really do not know much about how this is happening. We have no effective treatment for this condition, and many amongst us are directly or indirectly affected. It is heartbreaking we cannot do anything about it.
Citation:
Sébastien Tremblay Florian Pieper Adam Sachs Julio Martinez-Trujillo
Neuron: Volume 85, Issue 1, 7 January 2015, Pages 202–215
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Last Updated on January 9, 2015 by Marie Benz MD FAAD