title: Neural code alterations and abnormal time patterns in Parkinson's disease.
abstract: OBJECTIVE
  The neural code used by the basal ganglia is a current question in neuroscience, relevant for the understanding of the pathophysiology of Parkinson's disease. While a rate code is known to participate in the communication between the basal ganglia and the motor thalamus/cortex, different lines of evidence have also favored the presence of complex time patterns in the discharge of the basal ganglia. To gain insight into the way the basal ganglia code information, we studied the activity of the globus pallidus pars interna (GPi), an output node of the circuit.
  
  
  METHODS
  We implemented the 6-hydroxydopamine model of Parkinsonism in Sprague-Dawley rats, and recorded the spontaneous discharge of single GPi neurons, in head-restrained conditions at full alertness. Analyzing the temporal structure function, we looked for characteristic scales in the neuronal discharge of the GPi.
  
  
  RESULTS
  At a low-scale, we observed the presence of dynamic processes, which allow the transmission of time patterns. Conversely, at a middle-scale, stochastic processes force the use of a rate code. Regarding the time patterns transmitted, we measured the word length and found that it is increased in Parkinson's disease. Furthermore, it showed a positive correlation with the frequency of discharge, indicating that an exacerbation of this abnormal time pattern length can be expected, as the dopamine depletion progresses.
  
  
  CONCLUSIONS
  We conclude that a rate code and a time pattern code can co-exist in the basal ganglia at different temporal scales. However, their normal balance is progressively altered and replaced by pathological time patterns in Parkinson's disease.
authors: Institute of Neuroinformatics, ETH and University Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland. Institute for Neurological Research Raul Carrea, Fleni Institute, Movement Disorders section, Montañeses 2325, 1428, Buenos Aires, Argentina.
authors: Daniela Sabrina
authors: DS
authors: Andres
authors: Daniel
authors: D
authors: Cerquetti
authors: Marcelo
authors: M
authors: Merello
mesh_terms: D000200:Action Potentials; D000222:Adaptation, Physiological; D000818:Animals; D003198:Computer Simulation; D005260:Female; D005917:Globus Pallidus / Q000503:physiopathology*; D008297:Male; D008959:Models, Neurological; D009415:Nerve Net / Q000503:physiopathology*; D009473:Neuronal Plasticity; D016627:Oxidopamine; D010300:Parkinson Disease / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D016627:Oxidopamine