scholarly journals No apparent influence of psychometrically-defined schizotypy on orientation-dependent contextual modulation of visual contrast detection

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e2921 ◽  
Author(s):  
Damien J. Mannion ◽  
Chris Donkin ◽  
Thomas J. Whitford
Keyword(s):  
Clinical Sample ◽  
Negative Relationship ◽  
Relative Magnitude ◽  
Relative Effect ◽  
Apparent Difference ◽  
Target Pattern ◽  
Contextual Modulation ◽  
Contrast Detection ◽  
Visual Contrast ◽  
Relative Score

We investigated the relationship between psychometrically-defined schizotypy and the ability to detect a visual target pattern. Target detection is typically impaired by a surrounding pattern (context) with an orientation that is parallel to the target, relative to a surrounding pattern with an orientation that is orthogonal to the target (orientation-dependent contextual modulation). Based on reports that this effect is reduced in those with schizophrenia, we hypothesised that there would be a negative relationship between the relative score on psychometrically-defined schizotypy and the relative effect of orientation-dependent contextual modulation. We measured visual contrast detection thresholds and scores on the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE) from a non-clinical sample (N= 100). Contrary to our hypothesis, we find an absence of a monotonic relationship between the relative magnitude of orientation-dependent contextual modulation of visual contrast detection and the relative score on any of the subscales of the O-LIFE. The apparent difference of this result with previous reports on those with schizophrenia suggests that orientation-dependent contextual modulation may be an informative condition in which schizophrenia and psychometrically-defined schizotypy are dissociated. However, further research is also required to clarify the strength of orientation-dependent contextual modulation in those with schizophrenia.

Effects of Typical, Atypical, and No Antipsychotic Drugs on Visual Contrast Detection in Schizophrenia

2003 ◽  
Vol 160 (10) ◽  
pp. 1795-1801 ◽  
Author(s):  
Yue Chen ◽  
Deborah L. Levy ◽  
Summer Sheremata ◽  
Ken Nakayama ◽  
Steven Matthysse ◽  
...  
Keyword(s):  
Antipsychotic Drugs ◽  
Contrast Detection ◽  
Visual Contrast

scholarly journals Contrast Detection Learning Improves Visual Contrast Sensitivity of Cat

2010 ◽  
Vol 31 (2) ◽  
pp. 155-162
Author(s):  
Tian-Miao HUA ◽  
Zhen-Hua WANG ◽  
Jin-Wang XU ◽  
Jian-Gang DIAO
Keyword(s):  
Contrast Sensitivity ◽  
Contrast Detection ◽  
Visual Contrast ◽  
Visual Contrast Sensitivity

Timing and magnitude of electromyographic activity for two-joint arm movements in different directions

1991 ◽  
Vol 66 (5) ◽  
pp. 1594-1604 ◽  
Author(s):  
G. M. Karst ◽  
Z. Hasan
Keyword(s):  
Onset Time ◽  
Arm Movements ◽  
Preceding Paper ◽  
Distal Segment ◽  
Relative Magnitude ◽  
Time Difference ◽  
Emg Activity ◽  
Electromyographic Activity ◽  
Apparent Difference ◽  
Spatial Direction

1. We studied electromyographic (EMG) and kinematic features of self-paced human arm movements involving rotations about the shoulder and elbow joints. Movements were initiated from various positions and covered much of the reachable work space in the horizontal plane. The attempt was to characterize robust features of the relative timing and magnitude of the EMG activity at the two joints, and to correlate them with variables related to the initial and final positions. 2. The pattern of muscle activity at each joint was typically characterized by bursts of alternating agonist and antagonist activity, comparable with the three-burst pattern associated with single-joint movements. As the spatial direction of the target was altered, the magnitude of each burst was modulated over a continuous range. Modulation down to zero activity was observed, not only for later bursts, as has been shown in some cases of single-joint movements, but for the first agonist burst as well. 3. In the preceding paper we showed that the choice of agonists (i.e., flexors or extensors) at each joint is predictable on the basis of the target direction relative to the distal segment (psi). Here, we present quantitative analyses of initial agonist EMG activity at the shoulder and elbow, which reveal that the onset-time difference between agonists at the two joints also varied systematically with psi, and so did their relative magnitude. 4. For most target directions, initial EMG activity at the shoulder preceded that at the elbow by 5–40 ms. Exceptions were observed mainly for target directions near the transitions between initial flexor and initial extensor activity at the shoulder. In these cases the initial agonist activity at the shoulder was greatly reduced or, in some cases, appeared entirely suppressed, although the later bursts were present in their usual temporal alignment with the corresponding bursts at the elbow. 5. Antagonist onset at the elbow tended to precede antagonist onset at the shoulder, but the difference in timing did not vary consistently with psi. 6. Despite the consistency of initial agonist timing between the two joints, the agonist onset-time difference was poorly correlated with the apparent difference in the onset times of shoulder and elbow joint rotations. The latter difference, which is affected by mechanics, cannot therefore be imputed directly to the CNS.(ABSTRACT TRUNCATED AT 400 WORDS)

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