Inspecting a pattern of alternating dark and light bars makes it difficult to see a similar pattern presented afterward. This phenomenon can be used to isolate mechanisms responsive to bars of a given width. Our results suggest that the human visual system contains several different classes of size detectors, each maximally sensitive to visual targets with sizes in a particular range.

Adaptation, Ocular↗

PubMed1967

A model for after-effects of seen movement.

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Adaptation, Ocular↗

PubMedDate not supplied

Hysteresis in the perception of motion direction as evidence for neural cooperativity.

When elements of a parallel network, such as the human brain, are extensively interconnected, the network can exhibit 'cooperative behaviour'. Such behaviour, which is characterized by order-disorder transitions, multi-stable states, and a form of memory called 'hysteresis', has been observed in human stereopsis and has motivated models of stereopsis that incorporate cooperative networks. More recently, cooperative phenomena have also been observed in human visual motion perception. This report strongly supports a cooperative interpretation of motion perception by demonstrating hysteresis in the perception of motion direction. The results agree quantitatively with a mathematical model incorporating nonlinear excitatory and inhibitory interactions among direction-selective elements.

Humans↗

PubMedDate not supplied

Visual function after pan-retinal photocoagulation: a survey.

Thirty-five diabetic patients who had undergone pan-retinal photocoagulation were surveyed to determine the frequency and severity of visual difficulties they experience. Among the most frequent problems were difficulty adjusting to dim lighting, difficulty adjusting to bright lighting, and trouble in sorting dark colors. Judging distances, negotiating stairways, and avoiding obstacles were identified as having become more difficult since the laser treatment. According to a correlation analysis, the difficulties encountered in some important tasks, such as driving in the daytime, were highly related to visual acuity. However, many of the problems reported most frequently, and many of the problems whose frequency had increased the most since the laser therapy, were not related to acuity. Despite their many visual complaints, the patients expressed very positive attitudes toward the photocoagulation treatment.

Adaptation, Ocular↗