Spatiotemporal emergence of movement plans in the posterior parietal cortex during

eye-hand coordination

Arpan BanerjeeNYU

Sloan-Swartz Meeting 2008

Eye hand coordination

Target selection time Reaction time

Plan

Stimulus onset

Time

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

Recordings of spiking and LFP activity

Spikes

Rate(Hz)

Fields

Dean (In progress)Lazzaro (In progress)

Parietal reach region (PRR)Lateral intra-parietal area (LIP)

Voltage

Time (msec)

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

Modelling of LFP activity

Neural recordingarea

Autoregressive modelling with external input

Decoding Input

• Obtain the a’s (AR coefficients) by Burg’s algorithm

• Model order (p) selection using Akaike criterion

• Input decoded

• Amplitude and latency estimated trial by trial by maximizing the posterior

• Neural signal modeling for each direction of movement

• Accumulation of logarithm of likelihood ratio is obtained

Likelihood estimation

Target selection time estimation

• Accumulated log-likelihood ratios

Fields

104 msec

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

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.

Acknowledgements

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

Thank you!