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Spatio-temporal low-level neural networks account for visual masking.

Polat U, Sterkin A, Yehezkel O - Adv Cogn Psychol (2008)

Bottom Line: When a mask is presented, typically within less than 100 msec before or after the target, the response to the target is reduced.Thus, the masking effect depends on the spatial-temporal combination of these factors.We propose that masking effects, either suppression or facilitation, reflect integration into the spatial and the temporal domains of the feedforward response to the target and the lateral inputs evoked by the mask (excitatory and/or inhibitory).

View Article: PubMed Central - PubMed

Affiliation: Goldschleger Eye Research Institute, Tel-Aviv University, Sheba Medical Center, 52621 Tel-Hashomer, Israel.

ABSTRACT
T emporal masking is a paradigm that is widely used to study visual information processing. When a mask is presented, typically within less than 100 msec before or after the target, the response to the target is reduced. The results of our psychophysical and visual evoked potential (VEP) experiments show that the masking effect critically depends on a combination of several factors: (1) the processing time of the target, (2) the order of presentation of the target and the mask, and (3) the spatial arrangement of the target and the mask. Thus, the masking effect depends on the spatial-temporal combination of these factors. Suppression was observed when the mask was positioned within a spatial range that was found to evoke inhibition, and when the temporal separation between the target and the mask was short. In contrast, lateral facilitation was observed when the mask was presented at a spatial separation that did not evoke inhibition from the target's vicinity and with a temporal sequence that preceded the target, or when it was presented simultaneously with it, but not when the target preceded the mask. We propose that masking effects, either suppression or facilitation, reflect integration into the spatial and the temporal domains of the feedforward response to the target and the lateral inputs evoked by the mask (excitatory and/or inhibitory). Because the excitation evoked by the mask develops and propagates slowly from the mask's location to the target's location, it lags behind the response to the target. On the other hand, inhibition that is produced in the vicinity of the target evolves more rapidly and follows the onset and offset of the stimulus more closely. Thus, lateral excitation that overcomes the inhibition may facilitate the grouping of local elements into a global percept by increasing the survivability of the object and its accessibility for perceptual awareness.

No MeSH data available.


Related in: MedlinePlus

Evoked and predicted waveforms of visual evoked potentials. The average							waveforms (time courses of 1000 ms, 5 subjects) of the visual evoked							potentials (VEP) under three conditions are presented: the target							presented alone (T, red line), the mask presented alone (M, green line),							and the simultaneous masking (SM, blue line). The predicted time course							for the SM (T+M, blue dashed line) was calculated as the linear sum of T							and M. The time courses of T, F, and T+M are superimposed in the upper							panel; T and T+M – in the middle panel; T, M, and SM – in the lower							panel.
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Figure 6: Evoked and predicted waveforms of visual evoked potentials. The average waveforms (time courses of 1000 ms, 5 subjects) of the visual evoked potentials (VEP) under three conditions are presented: the target presented alone (T, red line), the mask presented alone (M, green line), and the simultaneous masking (SM, blue line). The predicted time course for the SM (T+M, blue dashed line) was calculated as the linear sum of T and M. The time courses of T, F, and T+M are superimposed in the upper panel; T and T+M – in the middle panel; T, M, and SM – in the lower panel.

Mentions: Figure 6 presents the time courses evoked by a low-contrast T presented alone, M presented alone, and SM, averaged for the 5 subjects, in comparison with the predicted SM response (T+M). The first positive amplitude (P1) of T is lower relative to P1 of M and SM. Moreover, P1 latency of T is delayed by 50 ms, compared with a P1 latency of F and SM (210 ms, 160 ms, 164 ms, T, M, and SM, respectively; averaged for 5 subjects) (Figure 6). Furthermore, a negative peak (N1) with a latency of 240 ms is evoked by M and SM, but not evoked by T.


Spatio-temporal low-level neural networks account for visual masking.

Polat U, Sterkin A, Yehezkel O - Adv Cogn Psychol (2008)

Evoked and predicted waveforms of visual evoked potentials. The average							waveforms (time courses of 1000 ms, 5 subjects) of the visual evoked							potentials (VEP) under three conditions are presented: the target							presented alone (T, red line), the mask presented alone (M, green line),							and the simultaneous masking (SM, blue line). The predicted time course							for the SM (T+M, blue dashed line) was calculated as the linear sum of T							and M. The time courses of T, F, and T+M are superimposed in the upper							panel; T and T+M – in the middle panel; T, M, and SM – in the lower							panel.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2864984&req=5

Figure 6: Evoked and predicted waveforms of visual evoked potentials. The average waveforms (time courses of 1000 ms, 5 subjects) of the visual evoked potentials (VEP) under three conditions are presented: the target presented alone (T, red line), the mask presented alone (M, green line), and the simultaneous masking (SM, blue line). The predicted time course for the SM (T+M, blue dashed line) was calculated as the linear sum of T and M. The time courses of T, F, and T+M are superimposed in the upper panel; T and T+M – in the middle panel; T, M, and SM – in the lower panel.
Mentions: Figure 6 presents the time courses evoked by a low-contrast T presented alone, M presented alone, and SM, averaged for the 5 subjects, in comparison with the predicted SM response (T+M). The first positive amplitude (P1) of T is lower relative to P1 of M and SM. Moreover, P1 latency of T is delayed by 50 ms, compared with a P1 latency of F and SM (210 ms, 160 ms, 164 ms, T, M, and SM, respectively; averaged for 5 subjects) (Figure 6). Furthermore, a negative peak (N1) with a latency of 240 ms is evoked by M and SM, but not evoked by T.

Bottom Line: When a mask is presented, typically within less than 100 msec before or after the target, the response to the target is reduced.Thus, the masking effect depends on the spatial-temporal combination of these factors.We propose that masking effects, either suppression or facilitation, reflect integration into the spatial and the temporal domains of the feedforward response to the target and the lateral inputs evoked by the mask (excitatory and/or inhibitory).

View Article: PubMed Central - PubMed

Affiliation: Goldschleger Eye Research Institute, Tel-Aviv University, Sheba Medical Center, 52621 Tel-Hashomer, Israel.

ABSTRACT
T emporal masking is a paradigm that is widely used to study visual information processing. When a mask is presented, typically within less than 100 msec before or after the target, the response to the target is reduced. The results of our psychophysical and visual evoked potential (VEP) experiments show that the masking effect critically depends on a combination of several factors: (1) the processing time of the target, (2) the order of presentation of the target and the mask, and (3) the spatial arrangement of the target and the mask. Thus, the masking effect depends on the spatial-temporal combination of these factors. Suppression was observed when the mask was positioned within a spatial range that was found to evoke inhibition, and when the temporal separation between the target and the mask was short. In contrast, lateral facilitation was observed when the mask was presented at a spatial separation that did not evoke inhibition from the target's vicinity and with a temporal sequence that preceded the target, or when it was presented simultaneously with it, but not when the target preceded the mask. We propose that masking effects, either suppression or facilitation, reflect integration into the spatial and the temporal domains of the feedforward response to the target and the lateral inputs evoked by the mask (excitatory and/or inhibitory). Because the excitation evoked by the mask develops and propagates slowly from the mask's location to the target's location, it lags behind the response to the target. On the other hand, inhibition that is produced in the vicinity of the target evolves more rapidly and follows the onset and offset of the stimulus more closely. Thus, lateral excitation that overcomes the inhibition may facilitate the grouping of local elements into a global percept by increasing the survivability of the object and its accessibility for perceptual awareness.

No MeSH data available.


Related in: MedlinePlus