Measuring the capacity for auditory system plasticity: An examination of performance gains during initial exposure to auditory-targeted cognitive training in schizophrenia

Early auditory processing abnormalities alter individual learning trajectories and sensitivity to computerized cognitive training in schizophrenia

BACKGROUND

Auditory system plasticity is a promising target for neuromodulation, cognitive rehabilitation and therapeutic development in schizophrenia (SZ). Auditory-based targeted cognitive training (TCT) is a 'bottom up' intervention designed to enhance the speed and accuracy of auditory information processing, which has been shown to improve neurocognition in certain SZ patients. However, the dynamics of TCT learning as a function of training exercises and their impact on neurocognitive functioning and therapeutic outcomes are unknown.

METHODS

Forty subjects (SZ, n = 21; healthy subjects (HS), n = 19) underwent comprehensive clinical, cognitive, and auditory assessments, including measurements of auditory processing speed (APS) at baseline and after 1-h of TCT. SZ patients additionally completed 30-hours of TCT and repeated assessments ~10-12 weeks later.

RESULTS

SZ patients were deficient in APS at baseline (d = 0.96, p < 0.005) relative to HS. After 1-h of TCT, analyses revealed significant main effects of diagnosis (d = 1.75, p = 0.002) and time (d = 1.04, p < 0.001), and a diagnosis × time interaction (d = 0.85, p = 0.02) on APS. APS learning effects were robust after 1-h in SZ patients (d = 1.47, p < 0.001) and persisted throughout the 30-h of training. Baseline APS was associated with verbal learning gains after 30-h of TCT (r = 0.51, p = 0.02) in SZ.

CONCLUSIONS

TCT learning metrics may have prognostic utility and aid in the prospective identification of individuals likely to benefit from TCT. Future experimental medicine studies may advance predictive algorithms that enhance TCT-related clinical, cognitive and functional outcomes.

Mismatch negativity predicts initial auditory-based targeted cognitive training performance in a heterogeneous population across psychiatric disorders

Auditory-based targeted cognitive training (ATCT) programs are emerging pro-cognitive therapeutic interventions which aim to improve auditory processing to attenuate cognitive impairment in a "bottom up" manner. Biomarkers of early auditory information processing (EAIP) like mismatch negativity (MMN) and P3a have been used successfully to predict gains from a full 40 h course of ATCT in schizophrenia (SZ). Here we investigated the ability of EAIP biomarkers to predict ATCT performance in a group of subjects (n = 26) across SZ, MDD, PTSD and GAD diagnoses. Cognition was assessed via the MATRICS Consensus Cognitive Battery (MCCB) and MMN/P3a were collected prior to completing 1 h of "Sound Sweeps," a representative ATCT exercise. Baseline and final performance over the first two levels of cognitive training served as the primary dependent variables. Groups had similar MMN, but the SZ group had attenuated P3a. MMN and MCCB cognitive domain t-scores, but not P3a, were strongly correlated with most ATCT performance measures, and explained up to 61% of variance in ATCT performance. Diagnosis was not a significant predictor for ATCT performance. These data suggest that MMN can predict ATCT performance in heterogeneous neuropsychiatric populations and should be considered in ATCT studies across diagnostically diverse cohorts.

Auditory discrimination and frequency modulation learning in schizophrenia patients: amphetamine within-subject dose response and time course

BACKGROUND

Auditory frequency modulation learning ('auditory learning') is a key component of targeted cognitive training (TCT) for schizophrenia. TCT can be effective in enhancing neurocognition and function in schizophrenia, but such gains require significant time and effort and elude many patients.

METHODS

As a strategy to increase and/or accelerate TCT-induced clinical gains, we tested the dose- and time-course effects of the pro-attentional drug, amphetamine (AMPH; placebo, 2.5, 5 or 10 mg po; within-subject double-blind, order balanced) on auditory learning in schizophrenia patients [n = 32; M:F = 19:13; age 42.0 years (24-55)]. To understand predictors and/or mechanisms of AMPH-enhanced TCT, we also measured auditory fidelity (words-in-noise (WIN), quick speech-in-noise (QuickSIN)) and neurocognition (MATRICS comprehensive cognitive battery (MCCB)). Some measures were also acquired from age-matched healthy subjects (drug free; n = 10; M:F = 5:5).

RESULTS

Patients exhibited expected deficits in neurocognition. WIN and QuickSIN performance at low signal intensities was impaired in patients with low v. high MCCB attention/vigilance (A/V) scores; these deficits were corrected by AMPH, maximally at 2.5-5 mg (d's = 0.79-1.29). AMPH also enhanced auditory learning, with maximal effects at 5 mg (d = 0.93), and comparable effects 60 and 210 min post pill. 'Pro-learning' effects of AMPH and AMPH-induced gains in auditory fidelity were most evident in patients with low MCCB A/V scores.

CONCLUSIONS

These findings advance our understanding of the impact of pro-attentional interventions on auditory information processing and suggest dose- and time-course parameters for studies that assess the ability of AMPH to enhance the clinical benefits of TCT in schizophrenia patients.

Auditory perceptual discomfort and low-hearing tolerance in the first episode psychosis

Awareness of perceptual and sensory changes that might occur in visual, auditory, proprioception, and other senses, in the early stages towards the First Episode Psychosis (FEP), and their subsequent sensorial evolution as the disturb progresses deeper into an acute episode, might be a key element for interrupting the process. In the present study, we investigated hearing discomfort/tolerance to 16 given sound streams. Sixteen people diagnosed with FEP, participated in the experiment. Sixteen frequency sweeps varying in modulation envelopes (sawtooth, sine), order (ascending, descending), duration (4s, 8s), and range (50–8000 Hz, 2–8 kHz) were presented randomly, but always in the same sequence, to FEP and healthy controls (HC). The level of discomfort was estimated by the participant by making a mark across a continuous line whose extremes read “nothing bad” (left) and “too bad” (right). Results showed that ascending sine pure frequency sweeps (p < 0.01) and descending sine pure frequencies sweeps (p < 0.01) caused the maximum discomfort in FEP. Other variables also showed differences between FEP and HC, and FEP were always more intolerant to such pure frequency sweeps than HC. We conclude that this might be useful for very early assessment of people at risk, people with FEP, and people with schizophrenia.

Implications for Early Diagnosis and Treatment in Schizophrenia Due to Correlation between Auditory Perceptual Deficits and Cognitive Impairment

It is indicated that auditory perception deficits are present in schizophrenia and related to formal thought disorder. The purpose of the present study was to investigate the association of auditory deficits with cognitive impairment in schizophrenia. An experimental group of 50 schizophrenia patients completed a battery of auditory processing evaluation and a neuropsychological battery of tests. Correlations between neuropsychological battery scores and auditory processing scores were examined. Cognitive impairment was correlated with auditory processing deficits in schizophrenia patients. All neuropsychological test scores were significantly correlated with at least one auditory processing test score. Our findings support the coexistence of auditory processing disorder, severe cognitive impairment, and formal thought disorder in a subgroup of schizophrenia patients. This may have important implications in schizophrenia research, as well as in early diagnosis and nonpharmacological treatment of the disorder.

Response to targeted cognitive training may be neuroprotective in patients with early schizophrenia

Individuals with schizophrenia exhibit widespread cortical thinning associated with illness severity and deficits in cognition. However, intact cortical thickness (CTh) may serve as a protective factor. The current study sought to examine changes in CTh in response to auditory targeted cognitive training (TCT) in individuals with recent onset schizophrenia. Participants underwent MRI scanning and a cognitive assessment before and after being randomly assigned to 40 h of either TCT (N = 21) or a computer games control condition (CG; N = 22) over 16 weeks. Groups did not differ at baseline on demographic variables or measures of CTh. At the level of group averages, neither group showed significant pre-post changes in CTh in any brain region. However, changes in CTh related to individual differences in treatment outcome, as improved global cognition in the TCT group corresponded to reduced cortical thinning in frontal, temporal, parietal, and occipital lobes. These relationships were not observed in the CG group. The current findings suggest that TCT may be neuroprotective in early schizophrenia, such that individuals who improved in response to training also showed a reduction in cortical thinning that may be otherwise hastened due to age and illness.

Memantine effects on auditory discrimination and training in schizophrenia patients

The uncompetitive low-affinity NMDA receptor antagonist, memantine, acutely increases electrophysiological measures of auditory information processing in both healthy subjects (HS) and patients with schizophrenia. Memantine effects on functional measures of auditory discrimination performance and learning are not known; conceivably, beneficial effects on these measures might suggest a role for memantine in augmenting the cognitive and functional impact of auditory targeted cognitive training (TCT). Here, carefully characterized HS (n = 20) and schizophrenia patients (n = 22) were tested in measures of auditory discrimination performance (words-in-noise (WIN), quick speech-in-noise (QuickSIN), gaps-in-noise) and auditory frequency modulation learning (a component of TCT) on 2 days about a week apart, after ingesting either placebo or 20 mg memantine po, in a double-blind, within-subject cross-over random order design. Memantine modestly enhanced functional measures of auditory discrimination in both schizophrenia patients (WIN) and HS (WIN and QuickSIN), as well as auditory frequency modulation learning in schizophrenia patients. These findings converge with a growing literature showing that memantine can enhance a range of metrics of auditory function. These properties could contribute to the apparent benefits of memantine as an adjunctive treatment in schizophrenia, and suggest that memantine might augment learning and potentially clinical gains from auditory-based TCT.

Gamma oscillations predict pro-cognitive and clinical response to auditory-based cognitive training in schizophrenia

Cognitive impairments are pervasive and disabling features of schizophrenia. Targeted cognitive training (TCT) is a "bottom-up" cognitive remediation intervention with efficacy for neurocognitive outcomes in schizophrenia, yet individual responses are variable. Gamma oscillatory measures are leading candidate biomarkers in the development of biologically informed pro-cognitive therapeutics. Forty-two schizophrenia patients were recruited from a long-term residential treatment facility. Participants were randomized to receive either 1 h of cognitive training (TCT, n = 21) or computer games (TAU, n = 21). All participants received standard-of-care treatment; the TCT group additionally completed 30 h of cognitive training. The auditory steady-state response paradigm was used to elicit gamma oscillatory power and synchrony during electroencephalogram recordings. Detailed clinical and cognitive assessments were collected at baseline and after completion of the study. Baseline gamma power predicted cognitive gains after a full course of TCT (MCCB, R² = 0.31). A change in gamma power after 1-h TCT exposure predicted improvement in both positive (SAPS, R² = 0.40) and negative (SANS, R² = 0.30) symptoms. These relationships were not observed in the TAU group (MCCB, SAPS, and SANS, all R² < 0.06). The results indicate that the capacity to support gamma oscillations, as well as the plasticity of the underlying ASSR circuitry after acute exposure to 1 h of TCT, reflect neural mechanisms underlying the efficacy of TCT, and may be used to predict individualized treatment outcomes. These findings suggest that gamma oscillatory biomarkers applied within the context of experimental medicine designs can be used to personalize individual treatment options for pro-cognitive interventions in patients with schizophrenia.

Auditory processing disorder may be present in schizophrenia and it is highly correlated with formal thought disorder

The present study investigates the presence of Auditory Processing Disorder (APD) in schizophrenia and its association with symptomatology, especially Formal Thought Disorder (FTD). 50 patients with schizophrenia and 25 matched healthy controls completed a battery of three auditory processing tests. Positive and Negative Syndrome Scale (PANSS) and Thought, Language and Communication (TLC) scale were used to assess clinical symptoms. The patient group was divided into two subgroups, according to FTD severity. Auditory processing performance of the control group and the patient group was evaluated. Correlations between auditory processing scores and TLC scores, as well as auditory processing scores and PANSS scores were examined. Most of the patients, especially those with FTD, had auditory deficits that can be classified as APD. Patients showed impaired performance compared to controls in all tests. Total severity and specific factors of FTD, as well as other clinical symptoms and symptom categories were correlated with auditory processing performance. We provided evidence that APD may be present in schizophrenia and that FTD, as well as other clinical symptoms are associated with auditory processing deficits. There are important clinical implications for non-pharmacological interventions and early diagnosis of schizophrenia.

CCR5 Is a Therapeutic Target for Recovery after Stroke and Traumatic Brain Injury

We tested a newly described molecular memory system, CCR5 signaling, for its role in recovery after stroke and traumatic brain injury (TBI). CCR5 is uniquely expressed in cortical neurons after stroke. Post-stroke neuronal knockdown of CCR5 in pre-motor cortex leads to early recovery of motor control. Recovery is associated with preservation of dendritic spines, new patterns of cortical projections to contralateral pre-motor cortex, and upregulation of CREB and DLK signaling. Administration of a clinically utilized FDA-approved CCR5 antagonist, devised for HIV treatment, produces similar effects on motor recovery post stroke and cognitive decline post TBI. Finally, in a large clinical cohort of stroke patients, carriers for a naturally occurring loss-of-function mutation in CCR5 (CCR5-Δ32) exhibited greater recovery of neurological impairments and cognitive function. In summary, CCR5 is a translational target for neural repair in stroke and TBI and the first reported gene associated with enhanced recovery in human stroke.

Individual Alpha Peak Frequency Moderates Transfer of Learning in Cognitive Remediation of Schizophrenia

OBJECTIVE

Meta-analyses report moderate effects across cognitive remediation (CR) trials in schizophrenia. However, individual responses are variable, with some participants showing no appreciable gain in cognitive performance. Furthermore, reasons for heterogeneous outcome are undetermined. We examine the extent to which CR outcome is attributable to near learning-direct gains in trained cognitive tasks-while also exploring factors influencing far transfer of gains during training to external cognitive measures.

METHOD

Thirty-seven schizophrenia outpatients were classified as CR responders and non-responders according to change in MATRICS Consensus Cognitive Battery composite score following 20 sessions of computer-based training. Metrics of near learning during training, as well as baseline demographic, clinical, cognitive, and electroencephalographic (EEG) measures, were examined as predictors of responder status.

RESULTS

Significant post-training improvement in cognitive composite score (Cohen's d = .41) was observed across the sample, with n = 21 and n = 16 classified as responders and non-responders, respectively. Near learning was evidenced by significant improvement on each training exercise with practice; however, learning did not directly predict responder status. Group-wise comparison of responders and non-responders identified two factors favoring responders: higher EEG individual alpha frequency (IAF) and lower antipsychotic dosing. Tested in moderation analyses, IAF interacted with learning to predict improvement in cognitive outcome.

CONCLUSION

CR outcome in schizophrenia is not directly explained by learning during training and appears to depend on latent factors influencing far transfer of trained abilities. Further understanding of factors influencing transfer of learning is needed to optimize CR efficacy.

Change in the Neural Response to Auditory Deviance Following Cognitive Therapy for Hallucinations in Patients With Schizophrenia

Adjunctive psychotherapeutic approaches recommended for patients with schizophrenia (SZ) who are fully or partially resistant to pharmacotherapy have rarely utilized biomarkers to enhance the understanding of treatment-effective mechanisms. As SZ patients with persistent auditory verbal hallucinations (AVH) frequently evidence reduced neural responsiveness to external auditory stimulation, which may impact cognitive and functional outcomes, this study examined the effects of cognitive behavioral therapy for voices (CBTv) on clinical and AVH symptoms and the sensory processing of auditory deviants as measured with the electroencephalographically derived mismatch negativity (MMN) response. Twenty-four patients with SZ and AVH were randomly assigned to group CBTv treatment or a treatment as usual (TAU) condition. Patients in the group CBTv condition received treatment for 5 months while the matched control patients received TAU for the same period, followed by 5 months of group CBTv. Assessments were conducted at baseline and at the end of treatment. Although not showing consistent changes in the frequency of AVHs, CBTv (vs. TAU) improved patients' appraisal (p = 0.001) of and behavioral/emotional responses to AVHs, and increased both MMN generation (p = 0.001) and auditory cortex current density (p = 0.002) in response to tone pitch deviants. Improvements in AVH symptoms were correlated with change in pitch deviant MMN and current density in left primary auditory cortex. These findings of improved auditory information processing and symptom-response attributable to CBTv suggest potential clinical and functional benefits of psychotherapeutical approaches for patients with persistent AVHs.

Deficits in Auditory and Visual Sensory Discrimination Reflect a Genetic Liability for Psychosis and Predict Disruptions in Global Cognitive Functioning

Sensory discrimination thresholds (i.e., the briefest stimulus that can be accurately perceived) can be measured using tablet-based auditory and visual sweep paradigms. These basic sensory functions have been found to be diminished in patients with psychosis. However, the extent to which worse sensory discrimination characterizes genetic liability for psychosis, and whether it is related to clinical symptomatology and community functioning remains unknown. In the current study we compared patients with psychosis (PSY; N=76), their first-degree biological relatives (REL; N=44), and groups of healthy controls (CON; N=13 auditory and visual/N=275 auditory/N=267 visual) on measures of auditory and visual sensory discrimination, and examined relationships with a battery of symptom, cognitive, and functioning measures. Sound sweep thresholds differed among the PSY, REL, and CON groups, driven by higher thresholds in the PSY compared to CON group, with the REL group showing intermediate thresholds. Visual thresholds also differed among the three groups, driven by higher thresholds in the REL versus CON group, and no significant differences between the REL and PSY groups. Across groups and among patients, higher thresholds (poorer discrimination) for both sound and visual sweeps strongly correlated with lower global cognitive scores. We conclude that low-level auditory and visual sensory discrimination deficits in psychosis may reflect genetic liability for psychotic illness. Critically, these deficits relate to global cognitive disruptions that are a hallmark of psychotic illnesses such as schizophrenia.

Divergence of subjective and performance-based cognitive gains following cognitive training in schizophrenia

BACKGROUND

Cognitive training is effective for improving cognitive performance among people with schizophrenia. An individual's perception of their own cognition is dissociable from performance on objective cognitive tests. Since subjective cognitive benefit may impact engagement, motivation, and satisfaction with time-intensive cognitive interventions, this study aimed to determine whether subjective cognitive difficulties improve in conjunction with cognitive gains following 30 h of cognitive training.

METHODS

Patients with schizophrenia or schizoaffective disorder (N = 46) were randomized to treatment as usual (TAU) or TAU augmented with auditory-targeted cognitive training (TCT). All participants completed assessment batteries at baseline and follow-up. As previously reported, the TCT group showed significant improvements in verbal learning and memory and reductions in auditory hallucinations relative to the TAU group.

RESULTS

Subjective cognitive difficulties did not significantly improve following TCT, even among TCT participants who showed improvements in cognitive performance (all ps > 0.05). Subjective cognitive difficulties were significantly associated with severity of depressive symptoms and hallucinations (r = 0.48 and r = 0.28, p < 0.001), but not global or specific domains of cognition (all rs < 0.1) at baseline. There were no significant relationships between change in subjective cognitive difficulties and change in cognitive or clinical variables (all ps > 0.05).

DISCUSSION

Patients with schizophrenia do not detect change in their cognition following cognitive training, even among those who showed robust gains in cognitive performance. Failure to detect improvement may undermine treatment engagement, motivation, and satisfaction. Translating score improvements on the cognitive exercises into tangible metrics, and providing ongoing, clinician-delivered feedback on performance may facilitate patient ability to detect improvements and improve motivation to engage with cognitive training interventions.

Impact of baseline early auditory processing on response to cognitive remediation for schizophrenia

BACKGROUND

Early auditory processing (EAP) has increasingly become a focus of efforts to identify biomarkers of treatment response in schizophrenia. EAP deficits lead to poor functional outcome via impaired cognition, and treatments that target EAP may drive downstream cognitive improvements. Assessment of baseline need provides an opportunity for cognitive remediation (CR) programs that give EAP training to personalize treatment and optimize its impact. This initial efficacy study examined the differential benefit of EAP training for those with and without baseline EAP deficits as defined by performance on the Tone Matching Test.

METHODS

103 outpatient adults diagnosed with schizophrenia or schizoaffective disorder were classified as having intact (48.5%) or impaired (51.5%) EAP and randomized to a CR program with restorative exercise plans that either included EAP training (N = 49) or did not (N = 54). Cognitive and functional outcomes were measured post-treatment and 3 months later.

RESULTS

Only in EAP impaired participants was there a significant benefit from EAP training on verbal learning. Treatment condition did not significantly impact global cognitive or functional outcomes for either EAP group. Cognitive gains partially mediated the relationship between gains in EAP and functional capacity.

CONCLUSION

These findings support the importance of addressing basic auditory deficits when attempting to remediate higher order auditory impairments such as verbal learning. In addition, they highlight the need for routine assessment of EAP in cognitive remediation participants, as well as the need for more effective programs to reverse these impairments.

A randomized controlled trial comparing a "bottom-up" and "top-down" approach to cognitive training in schizophrenia

The development of effective cognitive training (CT) interventions is critical for improving the daily lives of people with schizophrenia. At this point, it is unclear whether a so-called "bottom-up" or "top-down" CT approach is more beneficial for inducing cognitive gains and generalization in this population. The aims of this randomized controlled trial were to: 1) Compare the effects of these two types of training approaches on performance-based (MATRICS Consensus Cognitive Battery, MCCB) and neurophysiological (mismatch negativity, MMN) measures of cognition, and 2) Evaluate MMN as a potential predictor of treatment response. Ninety-nine patients with persistent schizophrenia (mean age of 51 and illness duration of 30 years) were randomly assigned in a 2:2:1 ratio to a "bottom-up" intervention that selectively targets basic auditory processing and verbal learning (Brain Fitness), a "top-down" intervention that targets a broad range of higher-order cognitive functions (COGPACK), or a control condition consisting of commercial computer games (Sporcle). Participants completed on average 30 h of training over 12 weeks. Despite demonstrated improvement on training tasks, we found no significant treatment effects on measures of neurocognition (MCCB), MMN, or functional capacity from either intervention. Interestingly, there was an association between an enhanced MMN response at 6 weeks and improved reasoning/problem solving at 12 weeks in the COGPACK group. Although this study had several methodological strengths, the results were mainly negative. It suggests that CT trials in schizophrenia should try to better understand mediators and moderators of treatment response to develop more personalized interventions.

Neurophysiologic measures of target engagement predict response to auditory-based cognitive training in treatment refractory schizophrenia

Cognitive impairment is a core feature of schizophrenia and a strong predictor of psychosocial disability. Auditory-based targeted cognitive training (TCT) aims to enhance verbal learning and other domains of cognitive functioning through "bottom-up" tuning of the neural systems underlying early auditory information processing (EAIP). Although TCT has demonstrated efficacy at the group level, individual response to TCT varies considerably, with nearly half of patients showing little-to-no benefit. EEG measures of EAIP, mismatch negativity (MMN) and P3a, are sensitive to the neural systems engaged by TCT exercises and might therefore predict clinical outcomes after a full course of treatment. This study aimed to determine whether initial malleability of MMN and P3a to 1-h of auditory-based TCT predicts improvements in verbal learning and clinical symptom reduction following a full (30-h) course of TCT. Treatment refractory patients diagnosed with schizophrenia were randomly assigned to receive treatment-as-usual (TAU; n = 22) or TAU augmented with TCT (n = 23). Results indicated that malleability (i.e., change from baseline after the initial 1-h dose of TCT) of MMN and P3a predicted improvements in verbal learning as well as decreases in the severity of positive symptoms. Examination of MMN and P3a malleability in patients after their first dose of TCT can be used to predict clinical response to a full course of treatment and shows promise for future biomarker-informed treatment assignment.

Targeted cognitive training improves auditory and verbal outcomes among treatment refractory schizophrenia patients mandated to residential care

Computerized targeted cognitive training (TCT) of auditory processing has been shown to improve verbal learning in several clinical trials of schizophrenia outpatients. Less is known, however, about the effectiveness of this promising intervention in more chronic, treatment-refractory patients who are treated in non-academic settings. This study aimed to determine whether TCT improves auditory processing, verbal learning, and clinical symptoms in SZ patients mandated to receive care at a locked residential rehabilitation center. Secondarily, potential factors that moderate TCT's effectiveness including age, symptom severity, antipsychotic medication load, and duration of illness were examined. Schizophrenia patients were randomized to treatment as usual (TAU; n = 22) or TAU augmented with TCT (TAU + TCT; n = 24). Outcomes included a measure of auditory perception (Word-In-Noise test, WIN), verbal learning domain scores from the MATRICS Consensus Cognitive Battery (MCCB), and clinical symptoms (Scale for the Assessment of Positive Symptoms, SAPS; Scale for the Assessment of Negative Symptoms, SANS). TCT produced significant improvements in auditory perception (d = 0.67) and verbal learning (d = 0.65); exploratory analyses revealed a statistically significant reduction in auditory hallucinations (d = -0.64). TCT's effects were only weakly, and mostly non-significantly, moderated by age, clinical symptoms, medication, and illness duration. These findings indicate that even highly symptomatic, functionally disabled patients with chronic illness benefit from this emerging treatment. Ongoing studies will examine the predictive utility of neurophysiological biomarkers and other characteristics assessed at baseline.

Mismatch Negativity is a Sensitive and Predictive Biomarker of Perceptual Learning During Auditory Cognitive Training in Schizophrenia

Computerized cognitive training is gaining empirical support for use in the treatment of schizophrenia (SZ). Although cognitive training is efficacious for SZ at a group level when delivered in sufficiently intensive doses (eg, 30-50 h), there is variability in individual patient response. The identification of biomarkers sensitive to the neural systems engaged by cognitive training interventions early in the course of treatment could facilitate personalized assignment to treatment. This proof-of-concept study was conducted to determine whether mismatch negativity (MMN), an event-related potential index of auditory sensory discrimination associated with cognitive and psychosocial functioning, would predict gains in auditory perceptual learning and exhibit malleability after initial exposure to the early stages of auditory cognitive training in SZ. MMN was assessed in N=28 SZ patients immediately before and after completing 1 h of a speeded time-order judgment task of two successive frequency-modulated sweeps (Posit Science 'Sound Sweeps' exercise). All SZ patients exhibited the expected improvements in auditory perceptual learning over the 1 h training period (p<0.001), consistent with previous results. Larger MMN amplitudes recorded both before and after the training exercises were associated with greater gains in auditory perceptual learning (r=-0.5 and r=-0.67, respectively, p's<0.01). Significant pretraining vs posttraining MMN amplitude reduction was also observed (p<0.02). MMN is a sensitive index of the neural systems engaged in a single session of auditory cognitive training in SZ. These findings encourage future trials of MMN as a biomarker for individual assignment, prediction, and/or monitoring of patient response to procognitive interventions, including auditory cognitive training in SZ.

Amphetamine Enhances Gains in Auditory Discrimination Training in Adult Schizophrenia Patients

Targeted cognitive training (TCT) of auditory processing enhances higher-order cognition in schizophrenia patients. TCT performance gains can be detected after 1 training session. As a prelude to a potential clinical trial, we assessed a pharmacological augmentation of cognitive therapy (PACT) strategy by testing if the psychostimulant, amphetamine, augments TCT gains in auditory processing speed (APS) in schizophrenia patients and healthy subjects (HS). HS and schizophrenia patients were tested in a screening session (test 1), followed by a double-blind crossover design (tests 2-3), comparing placebo vs amphetamine (10 mg; 7 d between tests). On each test day, 1 hour of Posit Science "Sound Sweeps" training was bracketed by 2- to 4-minute pre- and post-training assessments of APS. Training consisted of a speeded auditory time-order judgment task of successive frequency modulation sweeps. Auditory system "learning" (APS post- vs pre-training) was enhanced by amphetamine (main effect of drug: P < .002; patients: d = 0.56, P < .02; HS: d = 0.39, nonsignificant), and this learning was sustained for at least 1 week. Exploratory analyses assessed potential biomarker predictors of sensitivity to these effects of amphetamine. Amphetamine enhances auditory discrimination learning in schizophrenia patients. We do not know whether gains in APS observed in patients after 1 hour of TCT predict clinical benefits after a full course of TCT. If amphetamine can enhance the therapeutic effects of TCT, this would provide strong support for a "PACT" treatment paradigm for schizophrenia.

Practice and Learning: Spatiotemporal Differences in Thalamo-Cortical-Cerebellar Networks Engagement across Learning Phases in Schizophrenia

BACKGROUND

Understanding how practice mediates the transition of brain-behavior networks between early and later stages of learning is constrained by the common approach to analysis of fMRI data. Prior imaging studies have mostly relied on a single scan, and parametric, task-related analyses. Our experiment incorporates a multisession fMRI lexicon-learning experiment with multivariate, whole-brain analysis to further knowledge of the distributed networks supporting practice-related learning in schizophrenia (SZ).

METHODS

Participants with SZ were compared with healthy control (HC) participants as they learned a novel lexicon during two fMRI scans over a several day period. All participants were trained to equal task proficiency prior to scanning. Behavioral-Partial Least Squares, a multivariate analytic approach, was used to analyze the imaging data. Permutation testing was used to determine statistical significance and bootstrap resampling to determine the reliability of the findings.

RESULTS

With practice, HC participants transitioned to a brain-accuracy network incorporating dorsostriatal regions in late-learning stages. The SZ participants did not transition to this pattern despite comparable behavioral results. Instead, successful learners with SZ were differentiated primarily on the basis of greater engagement of perceptual and perceptual-integration brain regions.

CONCLUSION

There is a different spatiotemporal unfolding of brain-learning relationships in SZ. In SZ, given the same amount of practice, the movement from networks suggestive of effortful learning toward subcortically driven procedural one differs from HC participants. Learning performance in SZ is driven by varying levels of engagement in perceptual regions, which suggests perception itself is impaired and may impact downstream, "higher level" cognition.

Modeling Deficits From Early Auditory Information Processing to Psychosocial Functioning in Schizophrenia

IMPORTANCE

Neurophysiologic measures of early auditory information processing (EAP) are used as endophenotypes in genomic studies and biomarkers in clinical intervention studies. Research in schizophrenia has established correlations among measures of EAP, cognition, clinical symptoms, and functional outcome. Clarifying these associations by determining the pathways through which deficits in EAP affect functioning would suggest when and where to therapeutically intervene.

OBJECTIVES

To characterize the pathways from EAP to outcome and to estimate the extent to which enhancement of basic information processing might improve cognition and psychosocial functioning in schizophrenia.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional data were analyzed using structural equation modeling to examine the associations among EAP, cognition, negative symptoms, and functional outcome. Participants were recruited from the community at 5 geographically distributed laboratories as part of the Consortium on the Genetics of Schizophrenia 2 from July 1, 2010, through January 31, 2014. This well-characterized cohort of 1415 patients with schizophrenia underwent EAP, cognitive, and thorough clinical and functional assessment.

MAIN OUTCOME AND MEASURES

Mismatch negativity, P3a, and reorienting negativity were used to measure EAP. Cognition was measured by the Letter Number Span test and scales from the California Verbal Learning Test-Second Edition, the Wechsler Memory Scale-Third Edition, and the Penn Computerized Neurocognitive Battery. Negative symptoms were measured by the Scale for the Assessment of Negative Symptoms. Functional outcome was measured by the Role Functioning Scale.

RESULTS

Participants included 1415 unrelated outpatients diagnosed with schizophrenia or schizoaffective disorder (mean [SD] age, 46 [11] years; 979 males [69.2%] and 619 white [43.7%]). Early auditory information processing had a direct effect on cognition (β = 0.37, P < .001), cognition had a direct effect on negative symptoms (β = -0.16, P < .001), and both cognition (β = 0.26, P < .001) and experiential negative symptoms (β = -0.75, P < .001) had direct effects on functional outcome. The indirect effect of EAP on functional outcome was significant as well (β = 0.14, P < .001). Overall, EAP had a fully mediated effect on functional outcome, engaging general rather than modality-specific cognition, with separate pathways that involved or bypassed negative symptoms.

CONCLUSIONS AND RELEVANCE

The data support a model in which EAP deficits lead to poor functional outcome via impaired cognition and increased negative symptoms. Results can be used to help guide mechanistically informed, personalized treatments and support the strategy of using EAP measures as surrogate end points in early-stage procognitive intervention studies.