Reafference and attractors in the olfactory system during odor recognition. Kay, L. M., Lancaster, L. R., & Freeman, W. Int J Neural Syst, 7(4):489-95, 1996.
abstract   bibtex   
Graduate Group in Biophysics, University of California at Berkeley 94720, USA. LKAY@artemis.caltech.edu Olfactory bulb activity has been postulated to be chaotic, as measured in the EEG, and to be subject to an attractor with many "wings" enabling classification of different learned odor classes. Two parallel questions are thus addressed by the work presented here: (1) what is the evidence for attractors in the olfactory system, which can mediate learned odor classes? and (2) how does the olfactory system enter a specific attractor or attractor wing associated with the learned odor during the classification process? Both of these questions address the wider notion of endogenous activity preparing the system for an expected stimulus, which is at the basis of the reafference principle. By viewing the brain as a distributed complex dynamical system with global attractors, these questions can be answered together. Rats were implanted with bipolar macroelectrodes in the Olfactory Bulb (OB), Prepyriform Cortex (PPC), Entorhinal Cortex (EC), and Dentate Gyrus (DG), and then trained in an operant paradigm to press a bar for a reward in the presence of one odor and to receive no reward in the presence of another odor. Local Field Potentials (LFP) were recorded simultaneously from the structures during the operant task. We present evidence for three endogenous events: (1) preafference, which is manifested both by the EC entering an attractor and a mid-range signal (15-30 Hz) which appears to be passed from the EC to the OB just before the OB enters an attractor; (2) afference, where the OB enters an attractor during the odor recognition period of the experiment and the LFP recordings indicate that the OB drives the other structures in all frequency bands, especially the high gamma band (65-100 Hz) associated with the OB burst frequency; and (3) reafference or post-afference, which is accompanied by a lower frequency gamma band signal (40-60 Hz) originating in the PPC and passed to both the OB and the EC just before the onset of the motor response to the odor. We use a new method, NECTAR (Nonparametric Exact Contingency Table Association Routine), related to mutual information, to verify what is seen with coherence and phase estimates, the apparent driving of each structure at different times in the odor trials, and to display evidence for non-periodic attractors governing both individual physiological structures and the system of structures. This is the first evidence of an endogenous, limbic event associated with sensory perceptual tuning in a mammal. These results are also the first experimental confirmation that the attractors governing olfactory activity involve multiple sites in the olfactory/limbic system and implement the process of attention.
@article{ Kay_etal96,
  author = {Kay, L. M. and Lancaster, L. R. and Freeman, W.J.},
  title = {Reafference and attractors in the olfactory system during odor recognition},
  journal = {Int J Neural Syst},
  year = {1996},
  volume = {7},
  pages = {489-95},
  number = {4},
  abstract = {Graduate Group in Biophysics, University of California at Berkeley
	94720, USA. LKAY@artemis.caltech.edu 
	
	Olfactory bulb activity has been postulated to be chaotic, as measured
	in the EEG, and to be subject to an attractor with many "wings" enabling
	classification of different learned odor classes. Two parallel questions
	are thus addressed by the work presented here: (1) what is the evidence
	for attractors in the olfactory system, which can mediate learned
	odor classes? and (2) how does the olfactory system enter a specific
	attractor or attractor wing associated with the learned odor during
	the classification process? Both of these questions address the wider
	notion of endogenous activity preparing the system for an expected
	stimulus, which is at the basis of the reafference principle. By
	viewing the brain as a distributed complex dynamical system with
	global attractors, these questions can be answered together. Rats
	were implanted with bipolar macroelectrodes in the Olfactory Bulb
	(OB), Prepyriform Cortex (PPC), Entorhinal Cortex (EC), and Dentate
	Gyrus (DG), and then trained in an operant paradigm to press a bar
	for a reward in the presence of one odor and to receive no reward
	in the presence of another odor. Local Field Potentials (LFP) were
	recorded simultaneously from the structures during the operant task.
	We present evidence for three endogenous events: (1) preafference,
	which is manifested both by the EC entering an attractor and a mid-range
	signal (15-30 Hz) which appears to be passed from the EC to the OB
	just before the OB enters an attractor; (2) afference, where the
	OB enters an attractor during the odor recognition period of the
	experiment and the LFP recordings indicate that the OB drives the
	other structures in all frequency bands, especially the high gamma
	band (65-100 Hz) associated with the OB burst frequency; and (3)
	reafference or post-afference, which is accompanied by a lower frequency
	gamma band signal (40-60 Hz) originating in the PPC and passed to
	both the OB and the EC just before the onset of the motor response
	to the odor. We use a new method, NECTAR (Nonparametric Exact Contingency
	Table Association Routine), related to mutual information, to verify
	what is seen with coherence and phase estimates, the apparent driving
	of each structure at different times in the odor trials, and to display
	evidence for non-periodic attractors governing both individual physiological
	structures and the system of structures. This is the first evidence
	of an endogenous, limbic event associated with sensory perceptual
	tuning in a mammal. These results are also the first experimental
	confirmation that the attractors governing olfactory activity involve
	multiple sites in the olfactory/limbic system and implement the process
	of attention.}
}

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