Spatiotemporal emergence of movement plans in the posterior parietal cortex during eyehand coordinat

1
Spatiotemporal emergence of movement plans in the
posterior parietal cortex during eye-hand
coordination Arpan BanerjeeNYUSloan-Swartz
Meeting 2008
2
Eye hand coordination
Target selection time
Stimulus onset
Reaction time
Plan
Time
3
Working Hypotheses

• Either, eye-hand coordination requires shared
  target representations for saccades and reaches
  which may lead to correlation in target selection
  times across brain areas
• Or, coordination is primarily mediated by
  coupling between the movement plans after the
  target is selected

4
Recordings of spiking and LFP activity
Spikes
Rate (Hz)
Time (msec)
Fields
Voltage
Parietal reach region (PRR) Lateral
intra-parietal area (LIP)
Dean (In progress) Lazzaro (In progress)
5
Overview

• Primary Goal
• Unified analysis of spikes and fields to detect
  target selection times.
• Methods
• Statistical modeling of the specific patterns
  (variates) encoding movement directions.
• Decode the movement direction (and Target
  selection time) from the pattern (variate) given
  new data via likelihood ratio tests

Future direction RT
6
Modelling of LFP activity
Neural recording area
Autoregressive modelling with external input
7
Decoding Input

• Obtain the as (AR coefficients) by Burgs
  algorithm
• Model order (p) selection using Akaike criterion
• Input decoded
• Amplitude and latency estimated trial by trial by
  maximizing the posterior

8
Likelihood estimation

• Neural signal modeling for each direction of
  movement
• Accumulation of logarithm of likelihood ratio
  is obtained

9
Target selection time estimation

• Accumulated log-likelihood ratios

Fields
104 msec
10
Future directions

• Application of Sequential probability ratio tests
  to determine the target selection time from
  accumulated ratios Wald 1940
• Time variation of A R coefficients.
• Conditional intensity process will be considered
  for spike activity
• Extension to multivariate recordings

11
Summary

• Target selection time can be computed
  simultaneously from fields and spikes in a
  unified framework.
• Covariation of target selection times across
  different brain areas and with saccade and reach
  reaction times can be used to understand the
  coupling between eye and hand movements.

12
Acknowledgements

• Dr. Bijan Pesaran
• Stephanie Lazzaro
• Dr. Heather Dean
• Boris Revechkis
• Sam Gershman
• Eva Tsui
• Adam Weiss
• The Swartz Foundation

Thank you!