Psychophysiological Assessment within the NRLC
The NRLC has an active program of psychophysiological research that is focused on discovering the physiological substrates of behavioral performance.
The physiological recording studio is housed in a suite of offices in the heart of the NRLC building. This custom-construction suite allows for physiological recording within a tightly controlled recording environment. Scalable lighting and temperature control make this an optimal environment for physiological recording.
Domains of Psychophysiological Research
Researchers within the NRLC have a rich history of human psychophysiological research that brings together techniques including cortical measured event related potentials (e.g. P300) and evoked potentials (e.g. Auditory Intensity Dependence), as well as measures of acoustic startle response and autonomic function (blood pressure, heart rate response). Current areas of emphasis include:
- Human Acoustic Startle Response: Startle involves the electromyographic measurement of activation of the Orbicularis Oculi in reaction to rapid-onset, intense stimulation. In this procedure, we measure the magnitude of muscle activity of an involuntary eyeblink that is produced by a brief, but loud (e.g. 105 dB) noise. The response involves the contraction of muscles to prepare for escape or danger. As such the startle response is a noninvasive measure of information transfer from sensory receptors to motor effectors in mammals including humans.
- Prepulse Inhibition (PPI) of the Human Acoustic Startle Response: The startle response can be modified by exposure to a non-startling stimulus immediately before the startle-eliciting stimulus. For instance, if a noise (e.g. 70 dB) is presented just before a loud tone (e.g. 105 dB), then the size of the involuntary eyeblink may be significantly reduced. This attenuation is occurs because the processing of the initial (non-startling) stimulus is coupled with a sensorimotor gating mechanism that protects processing from being interrupted by the normally startling stimulus. Sensorimotor gating, represent an early stage of stimulus evaluation, acts as a perceptual filter that allows some stimuli to pass through for further processing while filtering out other stimuli. Problems with sensorimotor gating can allow higher order processing centers to be overwhelmed by irrelevant information, which leading to inefficient cognitive processing and expression of pre-potent responding.
- Affective Modulation of the Human Acoustic Startle Response: The startle response can be modified by pre-exposure to stimuli that have some affective quality. Generally, unpleasant stimuli augment the startle response and pleasant stimuli attenuate the response, relative to neutral conditions. There are standardized stimuli sets that available for manipulating the affective quality for this paradigm. Disruption of valence modulation has been shown to be important to the understanding of physiological effects of alcohol intoxication and physiological reactivity in psychopathic samples.
- P300: The P300 is a cortical event-related potential elicited by presentation of some deviant (rare) stimulus within a broader chain of stimuli. The magnitude of the P300 response is thought to reflect basic aspects of information processing such as allocation of attentional resources and context updating. The NRLC's interest in P300 has been used as an endophenotype measure of externalizing behavior disorders.
NRLC Psychophysiological Recording Equipment
The NRLC employs a wide range of hardware and software systems for our psychophysiological studies. Current research includes human acoustic startle, prepulse inhibition, and event related potentials (P300). We also have the capacity for impedance cardiography, blood pressure, and skin conductance measurements.
We currently utilize the following systems in our research:
-Biopac MP150 data acquisition and analysis system
-Neuroscan NuAmps 40 channel monopolar digital ERP recording system
-SCAN acquire and analysis software
-STIM2 stimulus presentation
-Electro-Cap International custom Ag/AgCl caps
-Ambu Neuroline electrodes
-Quest Technologies sound level meters