Comparing group performance on motion coherence and equivalent noise tasks.

<p>Schizophrenia and control group performances were compared using a series of one-way analyses of covariance with IQ scores included as a covariate. These analyses were undertaken on filtered data. See text however for details of analyses undertaken on non-filtered (raw) data with and without IQ included as a covariate. F = F-statistic; d.f. = degrees of freedom; <i>p</i> = significance level; Partial-η² = effect size; Th = motion coherence threshold; σ_int = internal noise; <i>n</i>_samp = sampling.</p><p>Comparing group performance on motion coherence and equivalent noise tasks.</p

Psychophysical procedures.

<p>(A) Example high (100%) and low (20%) coherence motion stimuli. Signal dots are shown in white and noise dots in black. Directions of motion are indicated by the orientation of the arrow-heads. (Note: in the actual experiment all dots were white). Below each example stimulus is shown the corresponding idealised distribution of signal values (solid black line) and noise values (dark grey shaded region). In the coherence task, noise was increased by changing the proportion of signal to noise dots. (B) Zero and high noise motion stimuli, with corresponding distributions of motion directions presented below. (C) The equivalent noise fit (solid black line) is constrained by two data-points: the ‘zero noise’ threshold, which represents the minimum directional offset that can be reliably discriminated, and the ‘high noise’ threshold, which represents the maximum level of noise that can be tolerated while discriminating between large directional offsets (±45°). The fitting-function (inset in C) has two parameters: internal noise and global sampling. (D) and (E) show zero and high noise orientation and size stimuli, for orientation and size judgements, respectively. The schematics below show corresponding distributions of orientations / sizes. In (A, B, D &amp; E), the reference direction / orientation / size is denoted by a vertical black dotted line; the average signal direction / orientation / size is circled.</p

Clinical data for the participants with schizophrenia.

<p>The following information is provided: diagnosis (Diag; SZ = schizophrenia; PS = Paranoid schizophrenia), medication (Med), medication type (Type: 1st = first generation antipsychotic; 2nd = second generation antispsychotic), medication dose (Dose: chlorpromazine equivalent in mg/day), intelligence quotient (IQ / NART score), total scores for the entire PANSS test (tPANSS), total scores for the positive symptoms of the PANSS test (tPSS), total scores for the negative symptoms of the PANSS test (tNSS), total scores for the general symptoms of the PANSS test (tGSS), scores on a cognitive factor which overlaps heavily with the concept of disorganization syndrome (tDIS) and scores for item P2 on the PANSS test, “conceptual disorganization” (DIS).</p><p>Clinical data for the participants with schizophrenia.</p

Partial and standard bivariate correlations between psychophysical performance and clinical measures / IQ.

<p>Partial correlations are shown for psychophysical and clinical variables for participants with schizophrenia whilst controlling for the effects of IQ scores (all rows except bottom two). Standard bivariate correlations are also shown for psychophysical measures and IQ scores (bottom two rows). R = Pearson’s correlation coefficient; <i>p</i> = significance level; Th = motion coherence threshold; σ_int = internal noise; <i>n</i>_samp = sampling. See legend to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117951#pone.0117951.t001" target="_blank">Table 1</a> for further details of abbreviations used for clinical measures.</p><p>Partial and standard bivariate correlations between psychophysical performance and clinical measures / IQ.</p

Coherence and equivalent noise plots.

<p>Group mean (A) coherence thresholds, (B) levels of internal noise and (C) sampling are shown for control participants and participants with schizophrenia. Error bars denote the standard error of the mean. Deg. = degrees. ** <i>p</i> = 0.01.</p

Results from Experiment 2.

<p>(a) Mean orientation discrimination thresholds for patients with SZ (red) and non-clinical controls (blue) in the three conditions tested in Experiment 2 (isolated Gabor, random flankers, contour-fragment). Black horizontal lines represent mean orientation thresholds. Note that in this graph higher y-values indicate <i>poorer</i> performance, whereas in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060951#pone-0060951-g002" target="_blank">Figure 2a</a> higher y-values indicate <i>better</i> performance. Patients’ thresholds in the isolated-Gabor condition are doubled compared to controls’, indicating reduced sensitivity to local orientation. (b) Log-ratios between thresholds in the isolated and crowded stimuli (i.e. log[isolated/random] and log[isolated/contour]). Both in the random flankers condition and in the contour-fragment condition patients show less crowding compared to controls.</p