Mental time in amnesia: evidence from bilateral medial temporal damage before and after recovery

The human mind is continuously involved in "projecting" the self in time in order to process past memories and predict future occurrences. "Self-projection" in time involves episodic and spatial memory, relying on medial-temporal structures, but also engages visuo-spatial imagery, relying on occipito-temporal structures, and self-location, relying on temporo-parietal structures. Here we had the rare opportunity to investigate the relation between self-projection in time and memory, using a novel behavioural paradigm, in a patient with subacute bilateral medial-temporal damage during a period of amnesia as well as after recovery. Despite her memory deficit the patient was able to "project" herself to past and future, yet with significant improvement after recovery. We discuss our findings with respect to the relations between episodic memory and medial-temporal structures with self-projection in time to past and future

Neurobiological signatures of L2 proficiency: Evidence from a bi-directional cross-linguistic study

Available online 12 November 2018Recent evidence has shown that convergence of print and speech processing across a network of primarily left-hemisphere regions of the brain is a predictor of future reading skills in children, and a marker of fluent reading ability in adults. The present study extends these findings into the domain of second-language (L2) literacy, through brain imaging data of English and Hebrew L2 learners. Participants received an fMRI brain scan, while performing a semantic judgement task on spoken and written words and pseudowords in both their L1 and L2, alongside a battery of L1 and L2 behavioural measures. Imaging results show, overall, a similar network of activation for reading across the two languages, alongside significant convergence of print and speech processing across a network of left-hemisphere regions in both L1 and L2 and in both cohorts. Importantly, convergence is greater for L1 in occipito-temporal regions tied to automatic skilled reading processes including the visual word-form area, but greater for L2 in frontal regions of the reading network, tied to more effortful, active processing. The main groupwise brain effects tell a similar story, with greater L2 than L1 activation across frontal, temporal and parietal regions, but greater L1 than L2 activation in parieto-occipital regions tied to automatic mapping processes in skilled reading. These results provide evidence for the shifting of the reading networks towards more automatic processing as reading proficiency rises and the mappings and statistics of the new orthography are learned and incorporated into the reading system.This paper was supported by the ERC Advanced grant awarded to Ram Frost (project 692502), the Israel Science Foundation (Grant 217/14 awarded to Ram Frost), and by the National Institute of Child Health and Human Development at the National Institutes of Health (RO1 HD 067364 awarded to Ken Pugh and Ram Frost, and PO1 HD 01994 awarded to Jay Rueckl)

Physiological correlates and predictors of functional recovery after chiasmal decompression

Background: The intrinsic abilities and limits of the nervous system to repair itself after damage may be assessed using a model of optic chiasmal compression, before and after a corrective surgical procedure. Methods: Visual fields (VFs), multifocal visual evoked potentials (mfVEP), retinal nerve fiber layer (RNFL) thickness, and diffusion tensor imaging were used to evaluate a patient before and after removal of a meningioma compressing the chiasm. Normally sighted individuals served as controls. The advantage of each modality to document visual function and predict postoperative outcome (2-year follow-up) was evaluated. Results: Postsurgery visual recovery was best explained by critical mass of normally conducting fibers and not associated with average conduction amplitudes. Recovered VF was observed in quadrants in which more than 50% of fibers were identified, characterized by intact mfVEP latencies, but severely reduced amplitudes. Recovery was evident despite additional reduction of RNFL thickness and abnormal optic tract diffusivity. The critical mass of normally conducting fibers was also the best prognostic indicator for functional outcome 2 years later. Conclusions: Our results highlight the ability of the remaining normally conductive axons to predict visual recovery after decompression of the optic chiasm. The redundancy in anterior visual pathways may be explained, neuroanatomically, by overlapping receptive fields. [There is an errata for this article. It can be found in: Journal of neuro-ophthalmology 2016 Volume 36(1) p. 114 at DOI: 10.1097/WNO.0000000000000373]5 page(s

Tracking second language immersion across time: Evidence from a bi-directional longitudinal cross-linguistic fMRI study

Available online 19 February 2021Parallel cohorts of Hebrew speakers learning English in the U.S., and American-English speakers learning Hebrew in Israel were tracked over the course of two years of immersion in their L2. We utilised a functional MRI semantic judgement task with print and speech tokens, as well as a battery of linguistic and cognitive behavioural measures prior to and after immersion, to track changes in both L1 and L2 processing. fMRI activation for print tokens produced a similar network of activation in both English and Hebrew, irrespective of L1 or L2 status. Significant convergence of print and speech processing was also observed in both languages across a network of left-hemisphere regions joint for both L1 and L2. Despite significant increases in behavioural measures of L2 proficiency, only a few signs of longitudinal change in L2 brain activation were found. In contrast, L1 showed widespread differences in processing across time, suggesting that the neurobiological footprint of reading is dynamic and plastic even in adults, with L2 immersion impacting L1 processing. Print/speech convergence showed little longitudinal change, suggesting that it is a stable marker of the differences in L1 and L2 processing across L2 proficiency.This paper was supported by the ERC Advanced grant (project 692502, L2STAT), the Israel Science Foundation (Grant 217/14), and by the National Institute of Child Health and Human Development at the National Institutes of Health (RO1 HD 067364)

Subthalamic theta activity: a novel human subcortical biomarker for obsessive compulsive disorder

Obsessive-compulsive disorder (OCD) is a common and serious psychiatric disorder. Although subthalamic nucleus deep brain stimulation (DBS) has been studied as a treatment for OCD patients the underlying mechanism of this treatment and the optimal method of stimulation are unknown. To study the neural basis of subthalamic nucleus DBS in OCD patients we used a novel, implantable DBS system with long-term local field potential sensing capability. We focus our analysis on two patients with OCD who experienced severe treatment-resistant symptoms and were implanted with subthalamic nucleus DBS systems. We studied them for a year at rest and during provocation of OCD symptoms (46 recording sessions) and compared them to four Parkinson’s disease (PD) patients implanted with subthalamic nucleus DBS systems (69 recording sessions). We show that the dorsal (motor) area of the subthalamic nucleus in OCD patients displays a beta (25–35 Hz) oscillatory activity similar to PD patients whereas the ventral (limbic-cognitive) area of the subthalamic nucleus displays distinct theta (6.5–8 Hz) oscillatory activity only in OCD patients. The subthalamic nucleus theta oscillatory activity decreases with provocation of OCD symptoms and is inversely correlated with symptoms severity over time. We conclude that beta oscillations at the dorsal subthalamic nucleus in OCD patients challenge their pathophysiologic association with movement disorders. Furthermore, theta oscillations at the ventral subthalamic nucleus in OCD patients suggest a new physiological target for OCD therapy as well as a promising input signal for future emotional-cognitive closed-loop DBS