Spatial frequency-dependent asymmetry of visual evoked potential amplitudes.

The extent to which pattern reversal evoked potential amplitudes are distributed symmetrically over the scalp was investigated as a function of stimulus spatial frequency. Nine right-handed male subjects viewed sinusoidal grating stimuli of 4.0 and 0.5 c/deg phase reversed every 900 msec. A visual half-field configuration enabled selective stimulation of the right- or left-hemisphere visual cortex. Evoked responses were recorded from the 2 cm above the inion (Oz) and at 7 and 13 cm lateral to Oz. Analyses of normalized evoked response amplitudes showed a significant asymmetry for the 4.0 c/deg stimulus; right-hemisphere amplitudes declined as a function of distance from the midline, while left-hemisphere amplitudes were greatest at the 7 cm recording site. No hemispheric differences were observed for the 0.5 c/deg stimulus; amplitudes for both hemispheres declined as a function of distance from the midline. The data are discussed in terms of hemispheric differences in morphology and functional asymmetries at early levels of sensory processing.

Moderate cold exposure shortens evoked potential latencies in humans.

Visual, auditory event-related potentials, and brainstem auditory-evoked responses were recorded in as many as six young male subjects in order to study the effects of moderate cold air exposure on central nervous system functioning. Evoked potentials were recorded during repeated 50-min exposures to air of 4 and 22 degrees C; these levels of exposure resulted in no change in rectal core temperature. Evoked potentials recorded during exposures to 4 degrees air displayed consistently shorter latencies compared to those recorded at 22 degrees, suggesting faster CNS processing of sensory stimuli in the cold. These results are consistent with recent investigations of cold-induced behavioral response changes which indicate that increased arousal may occur with moderate (nonhypothermic) cold exposure.

Adrenergic responses to cognitive activity in a cold environment.

Adrenergic responses during physical stress such as cold exposure have been reported to differ from those responses observed during cognitive activity. Both the separate and the combined effects of cold and cognitive activity on catecholamine activity were examined in six male subjects. Alterations in plasma epinephrine and norepinephrine showed different patterns as a function of exposure to a 4 degrees C cold environment, a cognitive performance assessment battery (PAB), and the two conditions combined. Plasma epinephrine was not altered by exposure to cold and only slightly increased by PAB performance when given at 23 degrees C. However, epinephrine was substantially elevated by exposure to combined cold and PAB. Heart rate changes paralleled observed changes in epinephrine. Norepinephrine release was predominantly increased by cold exposure and was not altered by PAB performance.

Repeated exposure to moderate cold impairs matching-to-sample performance.

To study effects of moderate cold (5 degrees C) on complex cognitive performance, subjects were exposed to cold while responding on a conditional discrimination task. The task required a correct choice of which of two simultaneously presented matrices matched a previously presented sample matrix. The effects of task performance in cold and ambient temperatures was examined on three repeated occasions, one pair of conditions per week. Responses accuracy was consistently impaired in each cold session. In addition, choice response latencies lengthened and sample response latencies decreased in all cold exposures. The data show that even moderate cold exposure that does not produce core hypothermia can impair performance of a complex cognitive task and that the magnitude of performance change is not attenuated by a brief series of cold exposures.

Assessment of desmopressin-enhanced cognitive function in a neurosurgical patient.

The vasopressin analog desmopressin (DDAVP) is known to enhance memory in animals and man but its precise mechanism of action is uncertain. We report the case of a patient who experienced chronic memory dysfunction with impaired job performance following transsphenoidal resection of a pituitary adenoma. A prospective double-blind, placebo-controlled trial of the effects of DDAVP was performed. Memory storage and recall improved with DDAVP treatment and declined within 1 week after drug withdrawal both by subjective and objective criteria. The Buschke Selective Reminding Test was clearly the most responsive out of a battery of standard memory testing paradigms employed to track the presence or absence of DDAVP treatment.

A comparison of biofeedback-mediated relaxation and group therapy in the treatment of chronic anxiety.

The authors compared treatment of chronic anxiety with biofeedback-mediated electromyographic (EMG) relaxation to treatment with group psychotherapy in a control group. Feedback patients were given two weeks of EMG relaxation training followed by two weeks of self-practice. Significant decreases were found in the feedback group in electromyogram levels, mood distrubance, trait anxiety, and (to a lesser extent) state anxiety; no such decreases occurred in the control group. The authors suggest that EMG feedback can be an important adjunct therapy for chronic anxiety.