Goal of the thesis

The main goal of my thesis was to assess whether information leaks into the peripheral systems as we plan to make an upcoming movement and to determine whether task context can modulate information that reaches the periphery. In this attempt, I studied eye and hand movements made by macaques and human subjects, respectively, under different task context and conditions. The broad objective for each chapter is as follows:

Aim1: Assessing central processes from the periphery

Towards this goal, I recorded from frontal eye fields (FEF) and neck muscles while macaque monkeys were involved in making saccadic eye movements in a memory-guided task. The delay period in this paradigm separated ‘where to’ from ‘when to’ initiate a movement. First, I tested whether information leaks into the periphery during this delay period. To be more specific I assessed whether the signals could be used to predict the spatial or temporal aspects of an upcoming saccade. Furthermore, I analysed whether the recruitment of motor units in the periphery could reflect central processes like motor planning during the delay period.

Main Objective: Can central processes be assessed from the periphery?

Specific aims: 1.1 Does information leak through to the periphery? 1.2 What information leaks through during the delay period? 1.3 Does information flow continuously into the periphery? 1.4 Can we assess motor plans from the periphery?

Also, to reconcile some of the issues raised in previous studies discussed during in the literature review, I also recorded from shoulder muscles (deltoid) while human subjects were instructed to reach and make hand movements to a peripheral target or apply isometric force on a robotic arm to move a cursor. By tracking the activity of putative motor units from surface EMG recordings, similar analyses were carried out for studies on hand movements as well.

Aim2: Leakage of information based on task context

The main objective was to test whether information that reaches the periphery could depend on different task contexts. In this endeavour, the first aim was to test whether the underlying architecture remains same for initiating eye movements under different conditions in both centre and periphery. The variability in time for initiating saccadic eye movements or reaction time could be due to early or late processing of information in the center and/or due to recruitment of motor units in periphery. To test this, I compared and looked at the (a) neural activity and (b) recruitment of motor units in relation to an accumulator framework during the reaction time for saccades in two different oculomotor tasks (i) in a delayed saccade task (ii) and an immediate saccade task.

Main Objective: How does task context modulate information that leaks into the periphery?

Specific aims: 1.1 To test the validity of LATER model for initiating movements and whether the computational architecture remains same in center and periphery? 1.2 To check whether task context effects the neural and activity of motor units? 1.3 To test whether one can parse out components of accumulation process centrally into different components?

Similar analyses were carried out on putative units captured from the periphery, to test whether similar results hold for initiating arm movements as well.