W. Keith Berg

The Tower of London spatial problem-solving task: enhancing clinical and research implementation.

Since its development in 1982, The Tower of London (TOL; Shallice, 1982) spatial problem-solving task has been increasingly employed in test batteries of executive functions. This task has served as a rich source of information on preparation, planning and processing, but a number of issues remain unaddressed in the literature: (1) the problem structure, or problem space of the task, (2) the impact of modifications from the original, Shallice TOL, and (3) the variety of performance measures that can be derived from the TOL. We present here an overview of these issues in the hope that it may lead to a more effective and reasoned use of the TOL task by clinical and nonclinical investigators, alike.

Diazepam blocks fear-enhanced startle elicited electrically from the brainstem

Startle-like responses were elicited electrically from the ventral cochlear nucleus (VCN) in darkness or in the presence of a light that had previously been paired with shocks. These startle-like responses were potentiated by the light and potentiation was selectively decreased by diazepam in a dose-related fashion (0.625 to 2.5 mg/kg). The benzodiazepine antagonist RO15-1788 attenuated the effect of diazepam. The data indicate that potentiation of electrically elicited startle behaves like acoustically elicited startle, providing further evidence that electrical elicitation of startle is a viable experimental technique.

Habituation and dishabituation of cardiac responses in 4-month-old, alert infants.

Abstract Heart rate responses to simple stimuli apparently shift from monophasic acceleration at birth to predominantly decelerative responses by 6 months. If this indicates a shift from defensive to orienting responses (OR), other characteristics of the OR might also be demonstrable in infants. In awake adults, OR characteristics include rapid habituation, dishabituation with stimulus change, and elicitation by stimulus offset. Thirty-two infants, alert throughout experimental sessions, received six trials of controlled rise time, 10-sec tones of moderate intensity. On Trials 7 and 8, frequency or temporal pattern was changed. All stimuli elicited marked decelerations which, in contrast to previously reported results, habituated within the six trials. Change in the stimulus elicited increased response magnitude or duration in all groups. Offset of continuous stimuli appeared to elicit small decelerations. These results indicate that cardiac decelerative responses are associated with other characteristics of orienting even at 4 months of age.

The startle response as an indicator of temporal summation

The present study assessed temporal summation of transient and sustained stimuli in the startle eyeblink response system. In two experiments, adult subjects received 95-dB(A), fast-rising broadband noise bursts of two types: (1) single stimuli varying in duration from 20 to 100 msec (Experiment 1) or 30 to 55 msec (Experiment 2) and (2) pairs of 3-msec bursts presented at interpulse intervals corresponding to the single stimulus durations. In addition, a single 3-msec pulse was used as an anchor point for both stimulus types. Though the temporal functions depended on whether startle amplitude or probability was assessed, both measures showed that temporal summation was similar for sustained stimuli and pulse pairs up to about 40 to 50 msec. Beyond this point, single stimuli maintained responding to 100 msec, whereas the second pulse of the pair quickly lost its effect. The results indicate that, although startle is influenced by summation of the sustained aspects of a stimulus, summation of transients produces an equivalent effect and does so with more acoustic efficiency (requires less energy). Response latency measures showed no significant summation with paired pulses, and only a narrow summation window for single stimuli. Thus, differential summation of sustained and transient information is demonstrated by all three response measures, but in different ways.

Cardiac orienting responses as a function of age

He art-rate changes, recorded from human Ss under conditions appropriate for eliciting orienting, were curvilinearly related to age and independent of differences in prestimulus heart rate. Deceleration was absent at birth, increased from 6 to 16 weeks, and lessened between 16 weeks and young adulthood.

Effects of acoustic rise time on heart rate response

Effects of acoustic rise time on heart-rate (HR) response were tested in two experiments. With 50- and 75-dB tones, effects were not clear-cut, but, at 90 dB, fast onsets produced an initial acceleration and slow onsets an initial deceleration. Results were discussed in terms of orienting and startle responses.

Cardiac orienting responses of 6- and 16-week-old infants☆

Abstract Since previous data suggested that the magnitude of orienting evidenced by cardiac deceleration increased over the first 16 weeks of life, 6- and 16-week-old infants were compared on various characteristics of orienting: habituation, dishabituation, and magnitude of deceleration to stimulus offset as well as to stimulus onset. Neither the change in stimulus following habituation trials nor the stimulus offset produced a large enough response to confidently evaluate age differences suggested by the data. Stimulus onset elicited a pronounced deceleration which for the two age groups was of equivalent magnitude on initial trials and declined similarly with stimulus repetition. It was suggested that similarity of the two age groups on these parameters was due to control of state within a narrow alert range, and that, in general, younger infants are less likely than older infants to show orienting when conditions for orienting are marginal.

The startle response and auditory temporal summation in neonates

The present study assessed temporal summation of transient and sustained stimuli in the startle eyeblink response system in neonates during quiet sleep. Subjects received 100-dB(A), fast-rising broadband noise bursts of two types: (a) single stimuli varying in duration from 20 to 100 ms and (b) pairs of 3-ms bursts presented at interpulse intervals corresponding to the single-stimulus durations. In addition, a single 3-ms pulse was used as an anchor point for both stimulus types. For startle amplitude, single stimuli were more effective than were paired stimuli, but the temporal summation functions were similar for the two types of stimuli. Response amplitude increased as stimulus duration/interval increased to 50 ms, but not beyond. For startle probability, temporal summation was similar for single and paired stimuli at 20 ms. Pairs of pulses were equally effective at 20, 35, and 50 ms, beyond which the second pulse was not effective. Increasing the duration of single stimuli from 20 to 35 ms resulted in increased probability, illustrating a contribution of sustained summation beyond that of transient summation. Response latency was generally greater for paired than for single stimuli. The results suggest that temporal summation of brief stimuli is deficient in the neonate. These data were compared to adult data from an analogous study, and suggest that the transient system is immature in infants, and that this immaturity is expressed differently by startle amplitude, probability, and latency.

Changes in electromyographic activity associated with occupational stress and poor performance in the workplace

A shift in the power spectrum of surface electromyographic (EMG) activity, recorded during machine-paced keyboard operation and indicative of localized muscle fatigue in the forearms, clearly distinguished two groups of operators who sorted mail in accordance with different work practices. The group exhibiting these fatigue-related changes in EMG activity also (1) had much greater difficulty in meeting the accuracy requirements of the keyboard function; (2) rated visual, mental, and keying-related workload as objectionably high; (3) exhibited greater tremor in a post-work test of hand steadiness; and (4) reported greater physical discomfort in the fingers, hands, wrists, and arms. These results demonstrate that physiological data can increase our understanding of the effects of occupational stress on performance in the workplace.

The effects of age and attention upon reflex inhibition

Previous research has suggested that reflex amplitude may be influenced by the direction of attention. The purpose of this investigation was to evaluate the effects of an attention-demanding visual reaction time task upon the elicitation of reflexes and modification of reflexes by an antecedent prestimulus in young and elderly adults. In young subjects, eyeblink inhibition was augmented by the task, yet there was no effect upon overall reflex amplitude. Elderly subjects showed no effect upon reflex inhibition while overall reflex amplitude was diminished by the task, independent of the amount of inhibition. In young subjects, the prestimulus also accentuated the initial decelerative component of a biphasic heart rate response. The reaction time task also served to augment this deceleration. The elderly heart rate response was not affected by the experimental conditions. These results provide evidence that reflex inhibition is modulated by attention. However, the relationship is complex, developmentally sensitive, and involves generalized attentive processes as well as selective attention toward specific stimuli or sensory modalities.