Arnold Wilkins

Frontal lesions and sustained attention

Neurological patients were presented with a succession of 2-11 stimuli which they were required to count, reporting the number in the series when it finished. The stimuli were binaural clicks, or pulses on the right or on the left index finger. Regardless of stimulus modality or lateralization, patients with lesions involving the right frontal lobe were impaired when the presentation rate was 1/sec. There was no corresponding impairment when the presentation rate was increased to 7/sec. It is argued that at slow rates when the task was monotonous patients with right-frontal lesions were less able than others to sustain attention voluntarily.

Photic- and Pattern-induced Seizures : A Review for the Epilepsy Foundation of America Working Group

Summary:  Purpose: This report summarizes background material presented to a consensus conference on visually provoked seizures, convened by the Epilepsy Foundation of America.

Fluorescent lighting, headaches and eyestrain

The weekly incidence of headaches among office workers was compared when the offices were lit by fluorescent lighting where the fluorescent tubes were operated by (a) a conventional switch-start circuit with choke ballast providing illumination that pulsated with a modulation depth of 43-49% and a principal frequency component at 100 Hz; (b) an electronic start circuit with choke ballast giving illumination with similar characteristics; (c) an electronic ballast driving the lamps at about 32 kHz and reducing the 100 Hz modulation to less than 7%. In a double-blind cross-over design, the average incidence of headaches and eyestrain was more than halved under high-frequency lighting. The incidence was unaffected by the speed with which the tubes ignited. Headaches tended to decrease with the height of the office above the ground and thus with increasing natural light. Office occupants chose to switch on the high-frequency lighting for 30% longer on average.

Rate of Reading Test®: its reliability, and its validity in the assessment of the effects of coloured overlays

A simple reading test that can be undertaken by disabled readers is described. The test is suitable for use in the optometric clinic, taking less than 2 minutes to administer per passage. Test-retest scores are acceptably reliable. The test reveals increases in the speed of reading when coloured overlays are used both (1) in children who have made long-term use of coloured overlays for reading, and (2) in children who will subsequently do so.

Conjoint frequency, category size, and categorization time

Two experiments which studied the time to decide whether or not a word was a member of a verbal category demonstrated that the results of several recent studies of categorization may be interpreted in terms of conjoint frequency (the frequency of cooccurrence of category and instance in English). The experiments showed that ( a ) instances with high conjoint frequency were categorized faster than instances of similar Thorndike-Lorge frequency but low conjoint frequency, and ( b ) when conjoint frequency was controlled, Thorndike-Lorge frequency did not reliably affect categorization time. It was also found that instances of large categories took longer to categorize than instances of small categories and that negative instances took longer to categorize when they were related to the category in terms of set.

Double‐masked placebo‐controlled trial of precision spectral filters in children who use coloured overlays

We selected 68 children who reported benefit from individually chosen sheets of coloured plastic placed upon the page when reading, and who used these regularly without prompting. These children viewed text illuminated by coloured light in an apparatus that allowed the separate manipulation of hue (colour) and saturation (depth of colour), at constant luminance. Many of the children reported improvements in perception when the light had a chromaticity within a limited range, which was different for each individual. A pair of plastic spectacle lenses (‘experimental’ lenses) was dyed so as to provide the appropriate chromaticity under conventional while (F3) fluorescent light. An additional pair was prepared having very similar colour but with a chromaticity outside the range in which perception was reported to improve (‘control’ lenses). Each pair was provided for 1 month in random order. The children kept diaries (36 completed) recording symptoms of eye‐strain and headache. The children and those responsible for their assessment were unable reliably to distinguish ‘experimental’ from ‘control’ lenses. Nevertheless, symptoms were less frequent on days when the ‘experimental’ lenses were worn (P < 0.003).

LED lighting flicker and potential health concerns: IEEE standard PAR1789 update

The IEEE Standards Working Group, IEEE PAR1789 “Recommending practices for modulating current in High Brightness LEDs for mitigating health risks to viewers” has been formed to advise the lighting industry, ANSI/NEMA, IEC, EnergyStar and other standards groups about the emerging concern of flicker in LED lighting. This paper introduces power electronic designers for LED lighting to health concerns relating to flicker, demonstrates that existing technologies in LED lighting sometimes provide flicker at frequencies that may induce biological human response, and discusses a few methods to consider when trying to mitigate unintentional biological effects of LED lighting. The paper represents on-going work in IEEE PAR1789 that is vital to designing safe LED lamp drivers.

Impaired contrast sensitivity in diabetic patients with and without retinopathy: a new technique for rapid assessment.

A simple technique is described for assessing the sensitivity of the human visual system to gratings at threshold contrast. The technique has advantages for clinical use in that it is (1) inexpensive, (2) quick to administer, (3) portable, and (4) relatively free from bias. Forty-two diabetic patients and 84 normal controls have been tested. Fifteen diabetic patients (6/20 with retinopathy and 9/22 without) had test scores more than two standard deviations below the norm for age-matched controls.

What Brings Intentions to Mind? An In Situ Study of Prospective Memory

In a naturalistic study, we aimed to uncover the relationship between thinking about and remembering intentions. Electronic badges allowed us to track the activities of subjects within their work environment. Over two weeks, subjects were asked to respond using a button on their badges (1) every two hours (Time task); (2) whenever they were in a particular room (Place task). In addition, whenever they thought about the task, they were asked to indicate this with their badges. Although subjects thought about the Time task more, they forgot to respond more often than in the Place task. In the Time task, there was a marked absence of thoughts about the task following successful remembering. When subjects remembered the Place task, thoughts increased with proximity to the target location. In both tasks, thoughts about intentions occurred more in places such as stairwells than in locations where people tended to settle. On the basis of these findings, possible mechanisms for prospective memory are discussed.

Selective impairment of semantic memory after temporal lobectomy

Abstract The impairment of semantic memory in patients with unilateral anterior temporal lobectomy was examined 1–21 yr after operation. Patients were asked to classify line drawings of objects or object names that appeared at a rate of one every 0.75 sec. Patients with left temporal removals were impaired at classifying objects as living or man-made, regardless of whether the objects were represented by drawings or by words. Classification of objects as larger or smaller than a chair was not impaired. The patients were also asked to name line drawings of objects presented at a similar rate, with or without a letter cue. Left temporal patients were impaired at naming uncued drawings. Patients with right temporal removals showed no deficits. The results were interpreted as suggesting that semantic memory is dissociable into verbal-amodal and non-verbal pictorial components, the former being impaired following left temporal lobectomy.