Gary D. Fisk

Driving after stroke: Driving exposure, advice, and evaluations

OBJECTIVE Little is known about the extent to which stroke survivors return to driving and the advice and/or evaluations they receive about driving. This study sought to estimate the prevalence of driving after stroke and to determine whether stroke survivors receive advice and evaluation about driving. DESIGN A convenience sample of stroke survivors was surveyed regarding driving status following stroke, driving exposure, advice received about driving, and evaluation of driving performance. PARTICIPANTS Two hundred ninety stroke survivors who were between 3 months to 6 years poststroke. RESULTS Thirty percent of stroke survivors who drove before the stroke resumed driving after the stroke. Stroke survivors are often poorly informed by health care professionals about driving, with 48% reporting that they did not receive advice about driving and 87% reporting that they did not receive any type of driving evaluation. Almost one third of poststroke drivers had high exposure, driving 6 to 7 days per week and/or 100 to 200 miles per week. CONCLUSIONS These findings suggest that many stroke survivors are making decisions about their driving capabilities without professional advice and/or evaluation. The results also suggest that rehabilitation professionals need to devote more attention and resources to driving issues when working with stroke survivors and their families.

Driving following traumatic brain injury: prevalence, exposure, advice and evaluations

Survivors of traumatic brain injury often have long-term sensory, cognitive and motor deficits that may impair vehicle operation. However, relatively little is known about the driving status and driving characteristics of brain injury survivors. To better understand driving following traumatic brain injury, a survey of driving status, driving exposure, advice received about driving and evaluations of driving competency was administered to a convenience sample of traumatic brain injury survivors (n = 83). The majority of survey participants had experienced either moderate or severe traumatic brain injuries based on the Glasgow Coma Scale. A total of 60% of the survey participants reported that they were currently active drivers. Most individuals (> 60%) who had returned to driving reported driving every day and more than 50 miles per week. Traumatic brain injury survivors frequently received advice about driving from family members, physicians or non-physician health care professionals, but over half (63%) had not been professionally evaluated for driving competency. The presence of high driving exposure, coupled with a lack of widespread driving fitness testing, suggests that some traumatic brain injury survivors have characteristics that may evaluate their risk for vehicle crashes. However, subsequent prospective studies that directly assess driver safety will be needed to confirm this possibility.

Impaired learning and memory in mature spontaneously hypertensive rats

In very old, normotensive rats, a disorganization occurs selectively in the retrosplenial cortex, and a similar disorganization occurs in this area in spontaneously hypertensive rats (SHR) at a much earlier age. Since this breakdown compromises a neural circuit involved in learning and memory, this study tests the hypotheses that these functions are disturbed in mature SHR and that they can be prevented or attenuated by long-term, anti-hypertensive therapy. SHR and Sprague Dawley rats (SD) at 3- and 12 months of age, and a group of SHR that had been normotensive from 3 to 12 months of age (CAP-SHR) were trained on an 8 arm radial maze task. Of the 12-month-old groups, SD reached criterion earliest (28 +/- 2 days) and made the least number of total errors. In comparison, 12-month-old SHR took significantly longer to reach criterion (39 +/- 2 days) and made nearly twice as many total errors. CAP-SHR were intermediate between the other two groups (32 +/- 2 days). Three-month-old SD learned the task at the same rate as the 12-month-old SD. In contrast, 3-month-old SHR learned the task significantly faster (21 +/- 1 days) and with fewer errors than any other group. These data indicate that, in SHR, learning and memory are compromised by 12 months of age, and that anti-hypertensive therapy with captopril partially prevents this decline.

Pressor and depressor sites are intermingled in the cingulate cortex of the rat.

Electrical stimulation of area infraradiata in the rat evokes transient changes in arterial pressure, but the locations that evoke these responses have not been mapped by neurochemical methods. To localize more specifically the regions of area infraradiata that modify cardiovascular activity, the present study measured cardiovascular responses to localized chemical stimulation of neurons in area infraradiata of urethane-anesthetized rats (n = 21). Microinjections (50-200 nl) of the glutamate agonist D,L-homocysteic acid into area infraradiata evoked both increases and decreases in arterial pressure and heart rate. Injections in the ventral subdivisions of rostral area infraradiata (IRa alpha and IRb alpha) produced cardiovascular responses with the highest probability and greatest magnitude. Of 53 injections in this area, 18 decreased arterial pressure and heart rate, whereas 4 increased arterial pressure and heart rate. In contrast to the results from the ventral subdivision of rostral infraradiata cortex, injections of D,L-homocysteic acid in the dorsal subdivision of rostral infraradiata cortex (IRc alpha) or any of the caudal subdivisions of area infraradiata (IR beta) produced less consistent changes in arterial pressure. To demonstrate that the general anesthesia did not significantly alter the evoked responses in this study, similar injections of D,L-homocysteic acid were made into area infraradiata of unrestrained, conscious rats (n = 10) and the responses were similar to the responses evoked in urethane-anesthetized rats. These results indicate that the ventral subdivisions of rostral area infraradiata (IRa alpha and IRb alpha) are more involved in cardiovascular regulation than other areas of infraradiata cortex (IRc alpha and IR beta), and that both pressor and depressor sites are present in both areas.

Useful field of view after traumatic brain injury

Background:Traumatic brain injury (TBI) survivors often have sensory and cognitive impairments that may interfere with driving ability. The Useful Field of View (UFOV) is a measure of visual information processing that is a good predictor of vehicle crash risk in older adults. Objective:The objective of this study was to explore the possibility that UFOV is compromised after TBI. Design:UFOV performance of 23 TBI survivors and 18 young adults without neurological impairment were compared. Conclusion:TBI survivors had higher UFOV scores than young adults, which indicated a greater functional loss of peripheral vision. The results suggest that the UFOV may be a valuable instrument for assessing driving readiness in TBI survivors.

Confidence in word detection predicts word identification: implications for an unconscious perception paradigm.

The present experiments extend the scope of the independent observation model based on signal detection theory (Macmillan & Creelman, 1991) to complex (word) stimulus sets. In the first experiment, the model predicts the relationship between uncertain detection and subsequent correct identification, thereby providing an alternative interpretation to a phenomenon often described as unconscious perception. Our second experiment used an exclusion task (Jacoby, Toth, & Yonelinas, 1993), which, according to theories of unconscious perception, should show qualitative differences in performance based on stimulus detection accuracy and provide a relative measure of conscious versus unconscious influences (Merikle, Joordens, & Stoltz, 1995). Exclusion performance was also explained by the model, suggesting that undetected words did not unconsciously influence identification responses.

Exclusion failure does not demonstrate unconscious perception II: Evidence from a forced-choice exclusion task

Systematic failure to perform exclusion (making a response that opposes the participants natural inclinations) for briefly displayed, masked words has been interpreted as evidence of unconscious perception. The present study required participants to make a forced-choice exclusion after viewing masked word targets. The forced-choice exclusion task was properly performed in all experiments, in contrast to previous studies that have utilized stem-completion as a dependent variable. The exclusion failure effects interpreted as unconscious perception in earlier studies appear to be caused by an insensitive dependent variable (stem-completion) rather than unconscious perception.

Valid distinctions between conscious and unconscious perception

In this commentary, we discuss the strengths and limitations of Snodgrass, Bernat, and Shevrin’s (2004) theory of unconscious perception. Our commentary centers on the value of signal detection theory (SDT) to understanding the unconscious perception controversy, a value that Snodgrass et al. for the most part agree with (i.e., that most approaches to studying unconscious perception are invalid because they have confounded the criterion for detection with the criterion for awareness). However, we believe that their model relies on a somewhat restricted application of SDT. We discuss how SDT can be better applied to provide the necessary tests to validate their model.

Exclusion failure does not demonstrate unconscious perception

Elevations in exclusion error rates (i.e., responding with the target stimulus despite instructions to the contrary) in experiments with masked, briefly presented stimuli have been attributed to unconscious perception. The present studies tested the validity of exclusion methods for studying unconscious perception. Experiment 1 replicated Merikle, Joordens, and Stolz (1995; Experiment 1) by showing more exclusion errors (exclusion failure) for masked word stimuli in a stem completion task. However, this experiment did not replicate the finding of fewer exclusion errors (exclusion success) at long stimulus durations. Experiments 2 and 3 showed that exclusion errors are accompanied by significant discrimination sensitivity to the target stimulus, which suggests conscious perception of the target stimulus. Experiments 3 and 4 demonstrated that the exclusion errors obtained from stem completion tasks depend in part on the exclusion method. Altogether, elevated exclusion failure does not provide an unambiguous demonstration of unconscious perception.

Common Neuropsychological Deficits Associated with Stroke Survivors' Impaired Performance on a Useful Field of View Test

Useful field of view is a measure of information processing in peripheral vision that has potential for predicting impaired driving performance. The present study was performed to examine whether common neuropsychological deficits resulting from stroke might be associated with useful field of view impairment. 46 stroke survivors had impaired useful field of view test performance when compared to individuals without stroke (t30.6= −4.33, p < .001). The impairments in useful field of view of stroke survivors were associated with impaired peripheral fields, slowed processing speeds, and diminished attention. Such impairment was not localized to lesions in any particular brain area. Results allow the inference that common neuropsychological impairments may have contributed to inefficient extraction of visual information from peripheral vision.