Mor Nahum

Reverse hierarchies and sensory learning

Revealing the relationships between perceptual representations in the brain and mechanisms of adult perceptual learning is of great importance, potentially leading to significantly improved training techniques both for improving skills in the general population and for ameliorating deficits in special populations. In this review, we summarize the essentials of reverse hierarchy theory for perceptual learning in the visual and auditory modalities and describe the theorys implications for designing improved training procedures, for a variety of goals and populations.

Low-Level Information and High-Level Perception: The Case of Speech in Noise

Auditory information is processed in a fine-to-crude hierarchical scheme, from low-level acoustic information to high-level abstract representations, such as phonological labels. We now ask whether fine acoustic information, which is not retained at high levels, can still be used to extract speech from noise. Previous theories suggested either full availability of low-level information or availability that is limited by task difficulty. We propose a third alternative, based on the Reverse Hierarchy Theory (RHT), originally derived to describe the relations between the processing hierarchy and visual perception. RHT asserts that only the higher levels of the hierarchy are immediately available for perception. Direct access to low-level information requires specific conditions, and can be achieved only at the cost of concurrent comprehension. We tested the predictions of these three views in a series of experiments in which we measured the benefits from utilizing low-level binaural information for speech perception, and compared it to that predicted from a model of the early auditory system. Only auditory RHT could account for the full pattern of the results, suggesting that similar defaults and tradeoffs underlie the relations between hierarchical processing and perception in the visual and auditory modalities.

Brain plasticity-based therapeutics

The primary objective of this review article is to summarize how the neuroscience of brain plasticity, exploiting new findings in fundamental, integrative and cognitive neuroscience, is changing the therapeutic landscape for professional communities addressing brain-based disorders and disease. After considering the neurological bases of training-driven neuroplasticity, we shall describe how this neuroscience-guided perspective distinguishes this new approach from (a) the more-behavioral, traditional clinical strategies of professional therapy practitioners, and (b) an even more widely applied pharmaceutical treatment model for neurological and psychiatric treatment domains. With that background, we shall argue that neuroplasticity-based treatments will be an important part of future best-treatment practices in neurological and psychiatric medicine.

From Comparison to Classification: A Cortical Tool for Boosting Perception

Humans are much better in relative than in absolute judgments. This common assertion is based on findings that discrimination thresholds are much lower when measured with methods that allow interstimuli comparisons than when measured with methods that require classification of one stimulus at a time and are hence sensitive to memory load. We now challenged this notion by measuring discrimination thresholds and evoked potentials while listeners performed a two-tone frequency discrimination task. We tested various protocols that differed in the pattern of cross-trial tone repetition. We found that best performance was achieved only when listeners effectively used cross-trial repetition to avoid interstimulus comparisons with the repeated reference tone. Instead, they classified one tone, the nonreference tone, as either high or low by comparing it with a recently formed internal reference. Listeners were not aware of the switch from interstimulus comparison to classification. Its successful use was revealed by the conjunction of improved behavioral performance and an event-related potential component (P3), indicating an implicit perceptual decision, which followed the nonreference tone in each trial. Interestingly, tone repetition itself did not suffice for the switch, implying that the bottleneck to discrimination does not reside at the lower, sensory stage. Rather, the temporal consistency of repetition was important, suggesting the involvement of higher-level mechanisms with longer time constants. These findings suggest that classification is based on more automatic and accurate mechanisms than interstimulus comparisons and that the ability to effectively use them depends on a dynamic interplay between higher- and lower-level cortical mechanisms.

A novel, online social cognitive training program for young adults with schizophrenia: A pilot study

BACKGROUND Pervasive social cognition deficits are evident early in the course of schizophrenia and are directly linked to functional outcome, making them an important target for intervention. Here, we tested the feasibility of use, and initiated the evaluation of efficacy, of a novel, neuroplasticity-based online training program (SocialVille) in young adults with schizophrenia. METHODS Schizophrenia patients (n=17) completed 24 hours of online SocialVille game play either from home or at a clinic, over a 6-10 week period. We examined training feasibility, gains on the SocialVille exercises relative to matched healthy controls (n=17), and changes on measures of social cognition, social functioning, global functioning and motivation. RESULTS Subjects adhered to training requirements, and rated SocialVille in the medium to high range in satisfaction, enjoyment, and ease of use. Subjects demonstrated significant, large improvements on the speeded SocialVille tasks, and small to moderate improvements on the working memory tasks. Post-training performance on the SocialVille tasks were similar to initial performance of the healthy controls. Subjects also showed improvements on standard measures of social cognition, social functioning, and motivation. No improvements were recorded for emotion recognition indices on the MSCEIT, or on quality of life scales. CONCLUSION This study provides an initial proof of concept for online social cognition training in schizophrenia. This form of training demonstrated feasibility and resulted in within-subject gains in social functioning and motivation. This pilot study represents a first step towards validating this training approach; randomized controlled trials, now underway, are designed to confirm and extend these findings.

Mechanisms of recovery of visual function in adult amblyopia through a tailored action video game

Amblyopia is a deficit in vision that arises from abnormal visual experience early in life. It was long thought to develop into a permanent deficit, unless properly treated before the end of the sensitive period for visual recovery. However, a number of studies now suggest that adults with long-standing amblyopia may at least partially recover visual acuity and stereopsis following perceptual training. Eliminating or reducing interocular suppression has been hypothesized to be at the root of these changes. Here we show that playing a novel dichoptic video game indeed results in reduced suppression, improved visual acuity and, in some cases, improved stereopsis. Our relatively large cohort of adults with amblyopia, allowed us, for the first time, to assess the link between visual function recovery and reduction in suppression. Surprisingly, no significant correlation was found between decreased suppression and improved visual function. This finding challenges the prevailing view and suggests that while dichoptic training improves visual acuity and stereopsis in adult amblyopia, reduced suppression is unlikely to be at the root of visual recovery. These results are discussed in the context of their implication on recovery of amblyopia in adults.

A Pilot Study of Cognitive Training in Clinical High Risk for Psychosis: Initial evidence of cognitive benefit

Individuals at clinical high risk (CHR) for psychosis have cognitive deficits that are associated with functional impairment and psychosis conversion (Giuliano et al., 2012). Targeted cognitive training (TCT) (i.e., intense, progressively difficult practice of a cognitive skill) improves cognition and daily functioning in schizophrenia (Wykes et al., 2011). TCT has been proposed as a preventive intervention for CHR, but research is minimal and optimal training parameters, including dose, intensity, and setting, are unknown. Because prolonged duration of untreated CHR symptoms can compromise outcome, rapid treatment response is essential (Fusar-Poli et al., 2009). However, ambiguous risk status, psychosis-related stigma, and practical scheduling problems can reduce treatment motivation and compliance. Without pilot data to guide intervention development, the randomized-controlled trials necessary to show efficacy of cognitive training in CHRmay be unsuccessful. This study investigated the feasibility and potential behavioral benefits of 40 h/8 weeks of computer-based TCT in a single group of CHR participants. Cognitive and functional outcome were assessed with measures recommended for clinical trials, including the MATRICS Consensus Cognitive Battery (MCCB) and Global Functioning (GF): Role and Social scales (Cornblatt et al., 2007). Training performance was analyzed to: verify the relationship between training engagement and treatment outcome; identify an early predictor of treatment response; and evaluate intervention dose.

Principles of Neuroplasticity-Based Rehabilitation

The purpose of this review is to summarize how our perspective about the neuroscience of brain plasticity, informed by perceptual, experimental, and cognitive psychology, has led to the designs of a new class of therapeutic tools developed to drive functionally distorted and damaged brains in corrective directions. How does neuroplasticity science inform us about optimal therapeutic program designs? How do we apply that science, using modern technology, to drive neurological changes that address both the neurobehavioral distortions and the resulting behavioral deficits that are expressed in specific neurological and psychiatric disorders? By what strategies can we achieve the strongest and most complete rehabilitative corrections? These are questions that we have extensively explored in our efforts to establish new medical applications of neuroplasticity-based therapeutics. Here, we summarize the state of this rapidly emerging area of translational neuroscience, beginning with an explanation of the scientific premises and strategies, then describing their implementation in therapeutic software to address two human illnesses: the treatment of social cognition deficits in chronic schizophrenia and in autism; and the amelioration of age-related functional decline using strategies designed to delay the onset of--and potentially prevent--Alzheimers Disease and related causes of dementia in aging.

Stimulus uncertainty and perceptual learning: similar principles govern auditory and visual learning

We examined the impact of variability in speech stimuli on improvement of general performance and on accessibility to low-level information as a function of practice. Listeners had to discriminate between two similar words in noise in two configurations that differed only in their low-level binaural information, which was either null or maximal. The difference in performance quantifies the use of binaural low-level information. These configurations were presented in three training protocols: in separate blocks; in a consistently interleaved manner; and in a randomly mixed manner. The first protocol enabled optimal use of the low-level binaural cues already at the first training session. The second, consistently interleaved protocol required more than one training session to reach the same performance. The final, mixed protocol did not enable optimal use of the low-level cues even after multi-session training. Interestingly, training with the first two protocols transferred to the mixed one. These results are in line with recent findings in the visual modality. In both modalities, the effects of variability on learning can be explained by the introduction of obstructions to a search mechanism going down along the sensory processing hierarchy, as suggested by the Reverse Hierarchy Theory.

Supplementing intensive targeted computerized cognitive training with social cognitive exercises for people with schizophrenia: An interim report

Objective: Individuals with schizophrenia demonstrate cognitive, social cognitive, and motivational deficits that contribute to impairment in real-world functioning. In the current study, we investigated the effects of supplementing computerized neurocognitive training with social cognitive exercises, as compared with neurocognitive training alone. Method: In this ongoing, double-blind, randomized controlled trial of 111 participants with psychosis, we compare the effects of supplementing intensive targeted cognitive training with social cognitive training exercises (TCT + SCT) with the effects of targeted cognitive training alone (TCT-only). Participants were assessed on cognition, symptoms, functional capacity, and functional outcomes, as well as social cognition and measures related to reward processing. Results: Both treatment groups showed significant improvement in multiple cognitive domains and improvement in functional capacity. However, as predicted, TCT + SCT group participants showed significant improvement in prosody identification and reward processing relative to TCT-only participants. Conclusions and Implications for Practice: Our findings indicate that supplementing intensive computerized cognitive training with social cognitive exercises in people with psychosis confers greater benefits in prosody identification and reward processing relative to cognitive training alone, even though both approaches drive significant improvements in cognition and functional capacity. Impairments in both prosody identification and reward processing have been associated with greater negative symptoms and poorer functional outcomes in schizophrenia, raising the possibility that this form of treatment may lead to better long-term outcomes than traditional cognitive training approaches. Follow-up assessments will determine whether results are durable and generalize over time to improvements in symptoms and functioning.