Biomedical subjects

P J Benson

Publications and source records attributed to P J Benson.

At least 19 recordsLinked to original sources

PubMed1999

Categorical perception of face actions: their role in sign language and in communicative facial displays.

Can face actions that carry significance within language be perceived categorically? We used continua produced by computational morphing of face-action images to explore this question in a controlled fashion. In Experiment 1 we showed that question--type--a syntactic distinction in British Sign Language (BSL)--can be perceived categorically, but only when it is also identified as a question marker. A few hearing non-signers were sensitive to this distinction; among those who used sign, late sign learners were no less sensitive than early sign users. A very similar facial-display continuum between "surprise" and "puzzlement" was perceived categorically by deaf and hearing participants, irrespective of their sign experience (Experiment 2). The categorical processing of facial displays can be demonstrated for sign, but may be grounded in universally perceived distinctions between communicative face actions. Moreover, the categorical perception of facial actions is not confined to the six universal facial expressions.

Adult↗

PubMed1999

Enhancing images of facial expressions.

Facial images can be enhanced by application of an algorithm--the caricature algorithm--that systematically manipulates their distinctiveness (Benson & Perrett, 1991c; Brennan, 1985). In this study, we first produced a composite facial image from natural images of the six facial expressions of fear, sadness, surprise, happiness, disgust, and anger shown on a number of different individual faces (Ekman & Friesen, 1975). We then caricatured the composite images with respect to a neutral (resting) expression. Experiment 1 showed that rated strength of the target expression was directly related to the degree of enhancement for all the expressions. Experiment 2, which used a free rating procedure, found that, although caricature enhanced the strength of the target expression (more extreme ratings), it did not necessarily enhance its purity, inasmuch as the attributes of nontarget expressions were also enhanced. Naming of prototypes, of original exemplar images, and of caricatures was explored in Experiment 3 and followed the pattern suggested by the free rating conditions of Experiment 2, with no overall naming advantage to caricatures under these conditions. Overall, the experiments suggested that computational methods of compositing and caricature can be usefully applied to facial images of expression. Their utility in enhancing the distinctiveness of the expression depends on the purity of expression in the source image.

Adult↗

PubMed1998

Short-latency ocular following of motion by monkeys during a fixation task.

Short-latency ocular following responses in monkeys, induced by first- and second-order motion during a fixation task, were sensitive to stimulus size, retinal eccentricity and motion duration. Latency of eye movements was no different for first- or second-order motion and simply marked the occurrence of movement in the visual field. Second-order motion produced higher velocity eye movements than did first-order motion. The velocity of eye movements was influenced by the orientation of second-order pattern components as well as their conspicuous energy. Even when partially suppressed by a fixation task, involuntary eye movements during the initial pursuit remain sensitive to several properties of visual motion.

Analysis of Variance↗

PubMed1998

Involuntary eye movements in response to first- and second-order motion.

We trained monkeys to maintain fixation while first- and second-order motion stimuli were displayed centrally in the visual field. Stimulus velocity, spatial frequency and contrast were varied to determine differences in patterns of involuntary eye movements elicited by random onset of stimulus motion. We observed different patterns of eye movement latency and velocity suggesting very early (< or = 100 ms) components of oculomotor activity are used to initiate smooth pursuit of object trajectory. Eye movement latency was insensitive to the complexity of stimulus motion, whereas second-order motion elicited faster eye movements than first-order motion. Instantaneous eye movement velocity might be related to the earliest stages of visual processing of component motion.

Animals↗

PubMed1998

Residual motion discrimination using colour information without primary visual cortex.

Previous studies have reported that some patients with damage to striate cortex retain the ability to detect monochromatic light and discriminate direction of achromatic movement in their blind visual fields. We investigated the residual chromatic visual capacity of a well-studied patient (GY) who has a unilateral lesion to striate cortex (V1). The data demonstrated that GY was able to detect and discriminate isoluminant colour targets presented in his blind hemifield. The velocity and contrast of chromatic moving stimuli affected GY's levels of conscious experience of movements he was able to discriminate. As the velocity or contrast was increased, his discrimination performance improved in line with rising visual awareness and judgement confidence. At isoluminance, GY continued to discriminate motion direction with above chance accuracy. These results indicate chromatic signals can also be used to process motion information in the absence of primary visual cortex.

Adult↗

PubMed1998

Gender-related differences in susceptibility of A/J mouse to benzo[a]pyrene-induced pulmonary and forestomach tumorigenesis.

Benzo[a]pyrene (BP) is a suspected human carcinogen and is known to produce tumors in the lung and forestomach of mice. Glutathione (GSH) S-transferases (GST) play a major role in the detoxification of the ultimate carcinogen of BP, (+)-anti-7,8-dihydroxy-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene ((+)-anti-BPDE). Previous studies have shown gender-related differences in the expression of GST isoenzymes in mice. The present study was designed to test the hypothesis whether gender-related differences in the expression of GST isoenzymes can affect the susceptibility of mice to BP-induced lung and forestomach tumorigenesis. The expression of pi class isoenzyme mGSTP1-1, which is highly efficient in the detoxification of (+)-anti-BPDE, was approximately 3.0- and 1.5-fold higher in the liver and forestomach of male A/J mouse, respectively, as compared with the female. The levels of other major GST isoenzymes, mGSTA3-3 (alpha class), mGSTM1-1 (mu class) and mGSTA4-4 (alpha class), were also significantly higher in the liver of the male mouse as compared with the female. While pulmonary mGSTP1-1 expression did not differ significantly between male and female A/J mice, the expression of mGSTA3-3, mGSTM1-1 and mGSTA4-4 was significantly higher (1.4-4.0-fold) in the lung of the male A/J mouse as compared with the female. At lower concentrations of BP (0.5 mg BP/mouse), the tumor incidence/multiplicity was significantly higher in the lung as well as in the forestomach of female mice as compared with male mice. For example, while 30% of the female mice developed pulmonary tumors 26 weeks after the first 0.5 mg BP administration, none of the male mice had tumors in their lungs. At higher doses of BP (1.5 mg BP/mouse), however, this differential was either abolished or relatively less pronounced. Our results suggest that up to a certain threshold of BP exposure the levels of GST isoenzymes may be an important determinant of susceptibility to BP-induced tumorigenesis in mice.

Animals↗

PubMed1998