The impact of early intervention for first episode psychosis on cognitive functioning.

IMPORTANCE: Impaired cognitive functioning is a core characteristic of schizophrenia, present from the onset of the illness and relatively stable thereafter. Despite evidence supporting the impact of early intervention services (EIS) on improving symptoms and functioning in first episode psychosis (FEP), controlled research has not examined its impact on cognitive functioning. OBJECTIVE: To evaluate the longitudinal course of cognitive functioning in FEP patients participating in a large, controlled study comparing EIS with usual services. METHODS: A total of 404 persons ages 15-40 years old with non-affective FEP participated in the Recovery After Initial Schizophrenia-Early Treatment Program. A cluster randomized controlled trial was conducted with 34 community mental health treatment centers across the U.S. randomized to provide either an EIS program (NAVIGATE) or usual Community Care (CC) to FEP patients for 2 years. Cognitive functioning was assessed with the Brief Assessment of Cognition in Schizophrenia (BACS) at baseline and 1- and 2-years later. RESULTS: Older participants (≥20 years old) in both treatment groups improved on all BACS tests. Younger participants (15-19) in NAVIGATE improved significantly more on Digit Sequencing (working memory) than those in CC, whereas both groups improved on most of the other BACS tests. Improvements in cognitive functioning occurred mostly over the first year and were correlated with reductions in symptom severity. DISCUSSION: EIS do not improve cognitive functioning more than usual care for older FEP patients but may improve working memory in younger FEP patients. Interventions targeting cognition may be required to enhance cognitive functioning in most FEP patients.

Feeling rushed? Perceived time pressure impacts executive function and stress.

Executive function (EF) is critical to everyday life, but it can be undermined by adverse psychological states like stress and negative affect. For example, inadequate time to perform a task is a common stressor that can disrupt EF. Although the impact of actual time pressure on EF has been established, little is known about how self-generated, perceived time pressure (PTP) affects EF in the absence of objective time limits. We chose Eriksen's Flanker task as an index of cognitive inhibition, a key component of EF, and we varied the interval between successive trials, the inter-trial interval (ITI), to proxy PTP. This manipulation strongly impacted task performance: shrinking the ITI to increase PTP diminished cognitive inhibition and increased both stress and negative affect. Subsequently lengthening the ITI to decrease PTP reversed nearly all of these effects, except stress, which persisted. Multilevel linear regression modeling revealed that ITI and stress predicted inhibition, and exploratory mediation modeling suggested that stress mediates the relationship between ITI and inhibition. These findings validate perceived time pressure as an empirical stressor and demonstrate EF's sensitivity to changes in PTP.

Perceptual timing precision with vibrotactile, auditory, and multisensory stimuli.

The growing use of vibrotactile signaling devices makes it important to understand the perceptual limits on vibrotactile information processing. To promote that understanding, we carried out a pair of experiments on vibrotactile, auditory, and bimodal (synchronous vibrotactile and auditory) temporal acuity. On each trial, subjects experienced a set of isochronous, standard intervals (400 ms each), followed by one interval of variable duration (400 ± 1-80 ms). Intervals were demarcated by short vibrotactile, auditory, or bimodal pulses. Subjects categorized the timing of the last interval by describing the final pulse as either "early" or "late" relative to its predecessors. In Experiment 1, each trial contained three isochronous standard intervals, followed by an interval of variable length. In Experiment 2, the number of isochronous standard intervals per trial varied, from one to four. Psychometric modeling revealed that vibrotactile stimulation produced poorer temporal discrimination than either auditory or bimodal stimulation. Moreover, auditory signals dominated bimodal sensitivity, and inter-individual differences in temporal discriminability were reduced with bimodal stimulation. Additionally, varying the number of isochronous intervals in a trial failed to improve temporal sensitivity in either modality, suggesting that memory played a key role in judgments of interval duration.

Feeling the Beat (and Seeing It, Too): Vibrotactile, Visual, and Bimodal Rate Discrimination.

Beats are among the basic units of perceptual experience. Produced by regular, intermittent stimulation, beats are most commonly associated with audition, but the experience of a beat can result from stimulation in other modalities as well. We studied the robustness of visual, vibrotactile, and bimodal signals as sources of beat perception. Subjects attempted to discriminate between pulse trains delivered at 3 Hz or at 6 Hz. To investigate signal robustness, we intentionally degraded signals on two-thirds of the trials using temporal-domain noise. On these trials, inter-pulse intervals (IPIs) were stochastic, perturbed independently from the nominal IPI by random samples from zero-mean Gaussian distributions with different variances. These perturbations produced directional changes in the IPIs, which either increased or decreased the likelihood of confusing the two pulse rates. In addition to affording an assay of signal robustness, this paradigm made it possible to gauge how subjects' judgments were influenced by successive IPIs. Logistic regression revealed a strong primacy effect: subjects' decisions were disproportionately influenced by a trial's initial IPIs. Response times and parameter estimates from drift-diffusion modeling showed that information accumulates more rapidly with bimodal stimulation than with either unimodal stimulus alone. Analysis of error rates within each condition suggested consistently optimal decision making, even with increased IPI variability. Finally, beat information delivered by vibrotactile signals proved just as robust as information conveyed by visual signals, confirming vibrotactile stimulation's potential as a communication channel.