Linear and nonlinear temporal interaction components of mid-latency auditory evoked potentials obtained with maximum length sequence stimulation.

A maximum length sequence (MLS) is a quasi-random sequence of clicks and silences that enables simultaneous recording of linear components and nonlinear temporal interaction components (NLTICs). NLTICs are produced when the stimulation rate is fast enough such that several stimuli occur within the memory length of the system. The present study was designed to characterise the NLTICs of auditory mid-latency responses (MLR).

The choice of distracting task can affect the quality of auditory evoked potentials recorded for clinical assessment.

Auditory evoked potential (AEP) recordings often require subjects to ignore the stimuli and stay awake. In the present experiment, early (ABR), middle (MLR), and late latency (LLR) AEPs were recorded to compare the effect of five different distracting tasks: (1) doing nothing eyes open, (2) reading, (3) watching a movie, (4) solving a three-digit sum, and (5) doing nothing eyes closed (or counting the stimuli for LLR). Results showed that neither the amplitudes nor the latencies of the ABR, MLR, or LLR were affected by task.

Linear and nonlinear changes in the auditory brainstem response of aging humans.

Objective: This experiment was designed to characterize the changes in linear and nonlinear temporal interactions in the aging auditory brainstem of humans using maximum length sequence (MLS) stimulation.

Methods: The MLS technique uses a quasi-random sequence of clicks and silences to determine the linear (linear averaging of single responses) and nonlinear (interactions between pairs or triplets of responses) temporal interactions in the auditory brainstem response (ABR). A group of 30 normal hearing females aged between 11 and 61years were tested.

Selective attention increases the temporal precision of the auditory N100 event-related potential.

Selective attention increases the amplitude of the averaged N100 event-related potential (ERP). This increase may result from more neurons responding to the stimulus or from the same number of neurons better synchronised with the stimulus, or both. We investigated the synchronization mechanism using a new response latency jitter measurement algorithm that performed well for all the signal-to-noise ratios obtained in the experiment.

The amplitude modulation of the quadriceps H-reflex in relation to the knee joint action during walking.

Previously the modulation of the quadriceps H-reflex has only been investigated in the initial part of the gait cycle, and it was suggested that the quadriceps H-reflex modulates with relative high reflex gain at heel contact and decreases during the subsequent part of stance (Dietz et al. 1990b). The objectives of the present study was to elaborate on the previous results by increasing the measurement resolution around heel contact and include additional measures in order to relate the H-reflex modulation to the mechanical function of the knee extensors throughout the gait cycle.

Timing of cortical excitability changes during the reaction time of movements superimposed on tonic motor activity.

Seated subjects were instructed to react to an auditory cue by simultaneously contracting the tibialis anterior (TA) muscle of each ankle isometrically. Focal transcranial magnetic stimulation of the leg area of the motor cortex (MCx) was used to determine the time course of changes in motor-evoked potential amplitude (MEP) during the reaction time (RT). In one condition the voluntary contraction was superimposed on tonic EMG activity maintained at 10% of maximal voluntary contraction.

Neural mechanisms involved in the functional linking of motor cortical points.

We sought to understand the basic neural processes involved in the functional linking of motor cortical points. We asked which of the two basic neural mechanisms, excitation or inhibition, is required to functionally link motor cortical points. In the ketamine-anaesthetized cat, a microstimulation electrode was positioned at a point (control point) that was identified by the following three characteristics of the EMG responses: the muscle(s) activated at threshold, any additional muscles recruited by supra-threshold stimulation, and their relative latency.