1,721,135 research outputs found
Cognitive rehabilitation in healty aging
No full textThe efficiency of interconnections among sensory neurons is reduced in the aged brain as a result of metabolic decline and subregulation of neural communication. Nevertheless, both behavioral and neuroimaging studies show that this cortical plasticity with negative consequences can be reversed through neurobehavioral restorative training. This results in improved normal and deficient visual processing in aging
The relationship between visual persistence and event perception in bistable motion display
No full textObservers viewed two alternating frames, each consisting of three rectangular bars displaced laterally by one cycle in one frame with respect to the other. At long interframe intervals (IFIs) observers perceived a group of three bars moving as a whole (group motion), and at short IFIs the overlapping elements in the two frames appeared stationary, while the third element appeared to move from one end of the display to the other (element motion). The upper temporal limit for perceiving element motion was reduced when bars with blurred edges were used and when either frame duration or bar size was increased. However, when inner and outer elements had different sizes, the element motion percept was dominant up to 230 ms IFI. These findings may be interpreted in terms of spatial tuning of motion mechanisms involved in the perception of bistable apparent motion
La retina e le vie afferenti
No full textLa percezione visiva a cura di F.Purghe, Stucchi N, Oliviero A. UTET UNIVERSITARI
Illusory boundary interpolation from local association field
No full textWe previously showed that interpolation between vertically misaligned luminance edges
of same polarity of contrast is preferred to that between co-linear edges of opposite polarity of contrast,
although it results in illusory tilt (Roncato and Casco, 2003). We here analyze the spatial conditions
that produce this illusory binding of vertically misaligned edges of light and dark tiles, alternated
in a row, and in counterphase with those in the rows above and below. We find that, independently
of scale and number of tiles in a row, the illusion is perceived when the vertical misalignment of
more than three tiles is smaller than or equal to 9 and the horizontal separation between co-linear
edges is smaller than or equal to 13. These short distances suggest that the underlying mechanism
is local. Both our phenomenological and psychophysical results support the notion of a local shortrange
association field, selective to contrast polarity, which produces a binding solution different from
that of a phase-independent long-range mechanism. We suggest that the occurrence of the illusion
at local-level is a result of the activation, within a local short-range association field, of units with
orientation different from that stimulated by the physical edges. These units are not inhibited when
they are close, iso-oriented and co-linear, and the misaligned edges from which they propagate have
the same contrast polarity. We found that horizontal and vertical spatial limits for the interpolation covary
but not such that their ratio is fixed, indicating that the two edges can be connected by projections
having a relatively wide range of orientations
Audiovisual bounce-inducing effect: attention alone does not explain why the discs are bouncing.
No full textTwo disks moving from opposite points in space, overlapping, and stopping at one another’s starting point
can be seen as either bouncing off one another or streaming through one another. With silent displays, observers
report streaming, whereas, if a sound is played when the disks are in the overlap region, observers report bouncing.
The change in perception is thought to be modulated by a lack of attention that inhibits the integration of
the motion signal when disks overlap and by the sound that increases the congruence of the display, in comparison
with a real elastic bounce. Here, we accompanied the disks’ motion with either a bounce-congruent sound (
a billiard ball) or with bounce-incongruent sounds (a water drop, a firework). When the sound was switched
on 200 msec before the disks’ overlap, (1) all the audiovisual displays induced more bounce responses than did
the silent display, but (2) the bounce-congruent sound induced more bounce responses than did the bounceincongruent
sounds. However, when the sound was switched on at the disks’ overlap, only the first result was
observed. These results highlight both the role of attention and that of sound congruence
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