PMID- 23486198
OWN - NLM
STAT- MEDLINE
DCOM- 20131216
LR  - 20130604
IS  - 1522-1598 (Electronic)
IS  - 0022-3077 (Linking)
VI  - 109
IP  - 11
DP  - 2013 Jun
TI  - Threshold mechanism for saccade initiation in frontal eye field and superior 
      colliculus.
PG  - 2767-80
LID - 10.1152/jn.00611.2012 [doi]
AB  - In an influential model of frontal eye field (FEF) and superior colliculus (SC) 
      activity, saccade initiation occurs when the discharge rate of either single 
      neurons or a population of neurons encoding a saccade motor plan reaches a 
      threshold level of activity. Conflicting evidence exists for whether this 
      threshold is fixed or can change under different conditions. We tested the 
      fixed-threshold hypothesis at the single-neuron and population levels to help 
      resolve the inconsistency between previous studies. Two rhesus monkeys performed 
      a randomly interleaved pro- and antisaccade task in which they had to look either 
      toward (pro) or 180 degrees  away (anti) from a peripheral visual stimulus. We isolated 
      visuomotor (VM) and motor (M) neurons in the FEF and SC and tested three specific 
      predictions of a fixed-threshold hypothesis. We found little support for fixed 
      thresholds. First, correlations were never totally absent between presaccadic 
      discharge rate and saccadic reaction time when examining a larger (plausible) 
      temporal period. Second, presaccadic discharge rates varied markedly between 
      saccade tasks. Third, visual responses exceeded presaccadic motor discharges for 
      FEF and SC VM neurons. We calculated that only a remarkably strong bias for M 
      neurons in downstream projections could render the fixed-threshold hypothesis 
      plausible at the population level. Also, comparisons of gap vs. overlap 
      conditions indicate that increased inhibitory tone may be associated with 
      stability of thresholds. We propose that fixed thresholds are the exception 
      rather than the rule in FEF and SC, and that stabilization of an otherwise 
      variable threshold depends on task-related, inhibitory modulation.
FAU - Jantz, Jay J
AU  - Jantz JJ
AD  - Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada.
FAU - Watanabe, Masayuki
AU  - Watanabe M
FAU - Everling, Stefan
AU  - Everling S
FAU - Munoz, Douglas P
AU  - Munoz DP
LA  - eng
GR  - MOP77734/Canadian Institutes of Health Research/Canada
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20130313
PL  - United States
TA  - J Neurophysiol
JT  - Journal of neurophysiology
JID - 0375404
SB  - IM
MH  - Action Potentials
MH  - Animals
MH  - Frontal Lobe/cytology/*physiology
MH  - Macaca mulatta
MH  - Male
MH  - Motor Neurons/physiology
MH  - Photic Stimulation
MH  - *Psychomotor Performance
MH  - *Saccades
MH  - *Sensory Thresholds
MH  - Superior Colliculi/cytology/*physiology
OTO - NOTNLM
OT  - antisaccade
OT  - inhibition
OT  - motoneuron
OT  - prosaccade
OT  - visuomotor neuron
EDAT- 2013/03/15 06:00
MHDA- 2013/12/18 06:00
CRDT- 2013/03/15 06:00
PHST- 2013/03/15 06:00 [entrez]
PHST- 2013/03/15 06:00 [pubmed]
PHST- 2013/12/18 06:00 [medline]
AID - jn.00611.2012 [pii]
AID - 10.1152/jn.00611.2012 [doi]
PST - ppublish
SO  - J Neurophysiol. 2013 Jun;109(11):2767-80. doi: 10.1152/jn.00611.2012. Epub 2013 
      Mar 13.