NEURO-11 : A computer system for relating neural spike trains to physiological and behavioral data

Abstract

NEURO-ll is a data acquisition, storage, retrieval, and analysis system for investigating the relationship between singleunit activity and behavior. Although other systems have been developed for the evaluation of neural data (Wyss & Handwerker, 1971; Roemer, Cegavske, Thompson, & Patterson, 1975), this system has unique capabilities for long-term acquisition over many data channels and subsequent analysis using a high-level computer language. The experiments for which NEURO·ll was designed examine the relationship of cerebellar neuronal firing patterns to several behavioral and physiological measures in the unanesthetized cat. At the outset of an experiment, one does not know the exact nature of the relationship between the activity of a neuron and sensori-motor events. The computer system presented here makes use of peri-event histograms and raster displays to uncover these relationships. These displays are constructed relative to a stimulus or motor reference point called a node. A node can be almost any event that is recorded simultaneously with the neuronal activity; for example, the increase of electromyographic activity (EMG) in a particular muscle, the placement of a limb in a predetermined location, or the presentation of a sensory stimulus. A peri-event histogram is constructed by choosing a node and examining the neuronal firing pattern forward and/or backward in time. Typically, the raster display and the associated cumulative histogram is generated by choosing a number of samples. Within a given data set there can be many different nodes. NEURO-ll allows the investigator to select nodes one at a time within the same data set and to test hypotheses about the relationships between nodes and neural data. System prerequisites. This system is designed for a PDP-II with 24K core storage, an RK-05 removal disk cartridge, and a Laboratory Peripheral System (LPS). The required LPS subsystems are the eight-channel analog-to-digital converter (A/D), the programmable clock, and the 16-bit digital I/O option. Other hardware includes a Tektronix 4010 graphics display terminal as the console device and a simple latch interface for the LPS digital input register. The latch interface stores digital data arriving on 16 digital input lines until the computer can read it. NEURO-ll runs under DEC DOS/BATCH-ll (V9-2OC) using the MACRO-ll assembler and FORTRAN compiler. Input program (ALLIN). The system consists of two programs: a data input program (ALLIN) written in assembly language and an interactive data retrieval, manipulation, and display program (ANA) written primarily in FORTRAN. The input program, ALLIN, was designed to efficiently encode and store a high volume of input data for a sustained period. The primary inputs are pulse (event) data occurring on the digital input lines. These digital events are the occurrences of neural spikes and stimulus or motor event markers. Analog voltages can be recorded on all or any combination of the eight A/D channels. The output of the program is a disk file which contains encoded input and control data. This file is later read and decoded by the analysis program (ANA). Data are organized into sessions which are partitioned into trials by means of a switch connected to one of the digital input lines. The disk address of each trial is stored in a trial directory so that any trial within a session is rapidly accessible. Data representation. The input program (ALLIN) generates four different types of data words: clock, digital event, AID, and time code words. Each type of data word is distinguishable by the value of its high-order 2 bits. The format of these words is shown in Figure 1. A clock word is generated and stored on the disk every 500 msec. The low-order 14 bits of this word