Montserrat Juncadella

Analysis of automated methods for spatial normalization of lesioned brains.

Normalization of brain images is a crucial step in MRI data analysis, especially when dealing with abnormal brains. Although cost function masking (CFM) appears to successfully solve this problem and seems to be necessary for patients with chronic stroke lesions, this procedure is very time consuming. The present study sought to find viable, fully automated alternatives to cost function masking, such as Automatic Lesion Identification (ALI) and Diffeomorphic Anatomical Registration using Exponentiated Lie algebra (DARTEL). It also sought to quantitatively assess, for the first time, Symmetrical Normalization (SyN) with constrained cost function masking. The second aim of this study was to investigate the normalization process in a group of drug-resistant epileptic patients with large resected regions (temporal lobe and amygdala) and in a group of stroke patients. A dataset of 500 artificially generated lesions was created using ten patients with brain-resected regions (temporal lobectomy), ten stroke patients and twenty five-healthy subjects. The results indicated that although a fully automated method such as DARTEL using New Segment with an extra prior (the mean of the white matter and cerebro-spinal fluid) obtained the most accurate normalization in both patient groups, it produced a shrinkage in lesion volume when compared to Unified Segmentation with CFM. Taken together, these findings suggest that further research is needed in order to improve automatic normalization processes in brains with large lesions and to completely abandon manual, time consuming normalization methods.

Frontal and associative visual areas related to visual hallucinations in dementia with Lewy bodies and Parkinson's disease with dementia.

Visual Hallucinations (VH) are among the core features of Dementia with Lewy Bodies (DLB), but are also very frequent in demented patients with Parkinsons Disease (PDD). The purpose of this study was to investigate the pattern of gray matter and cognitive impairment underlying VH in DLB and PDD. We applied voxel‐based morphometry and behavioral assessment to 12 clinically diagnosed DLB patients and 15 PDD patients. Subjects with VH showed greater gray matter loss than non‐hallucinators, specifically in the right inferior frontal gyrus (BA 45) in the DLB patients and in the left orbitofrontal lobe (BA 10) in the PDD patients. Comparing the two subgroups with VH, DLB patients had greater decrease of the bilateral premotor area (BA 6) than PDD patients. Furthermore, decreased volume in associative visual areas, namely left precuneus and inferior frontal lobe, correlated with VH in the DLB but not in PDD patients. VH were related to impaired verbal fluency, inhibitory control of attention and visuoperception in the DLB group and to visual memory in the PDD group. In conclusion, DLB and PDD patients with VH had more frontal gray matter atrophy than non‐hallucinators, the impairment being greater in the DLB group. The patterns of structural and functional correlations were different in both pathologies.

Music-Supported Therapy induces plasticity in the sensorimotor cortex in chronic stroke: A single-case study using multimodal imaging (fMRI-TMS)

Primary objective: Music-Supported Therapy (MST) has been developed recently in order to improve the use of the affected upper extremity after stroke. This study investigated the neuroplastic mechanisms underlying effectiveness in a patient with chronic stroke. Methods: MST uses musical instruments, a midi piano and an electronic drum set emitting piano sounds, to retrain fine and gross movements of the paretic upper extremity. Data are presented from a patient with a chronic stroke (20 months post-stroke) with residual right-sided hemiparesis who took part in 20 MST sessions over the course of 4 weeks. Results: Post-therapy, a marked improvement of movement quality, assessed by 3D movement analysis, was observed. Moreover, functional magnetic resonance imaging (fMRI) of a sequential hand movement revealed distinct therapy-related changes in the form of a reduction of excess contralateral and ipsilateral activations. This was accompanied by changes in cortical excitability evidenced by transcranial magnetic stimulation (TMS). Functional MRI in a music listening task suggests that one of the effects of MST is the task-dependent coupling of auditory and motor cortical areas. Conclusions: The MST appears to be a useful neurorehabilitation tool in patients with chronic stroke and leads to neural reorganization in the sensorimotor cortex.

Hippocampus-Dependent Strengthening of Targeted Memories via Reactivation during Sleep in Humans

Recent accumulating evidence in animals and humans has shown that memory strengthening occurs, at least partially, during sleep and relies on the covert reactivation of individual memory episodes. However, it remains to be determined whether the hippocampus critically promotes memory consolidation via the reactivation of individual memories during sleep. To investigate the hippocampal-dependent nature of this phenomenon in humans, we selected two groups of chronic temporal lobe epileptic (TLE) patients with selective unilateral (TLE+UHS) or bilateral (TLE+BHS) hippocampal sclerosis and a group of matched healthy controls, and we requested them to learn the association of sounds cueing the appearance of words. On the basis of other similar behavioral paradigms in healthy populations, sounds that cued only half of the learned memories were presented again during the slow-wave sleep stage (SWS) at night, thus promoting memory reactivation of a select set of encoded episodes. A memory test administered on the subsequent day showed that the strengthening of reactivated memories was observed only in the control subjects and TLE+UHS patients. Importantly, the amount of memory strengthening was predicted by the volume of spared hippocampus. Thus, the greater the structural integrity of the hippocampus, the higher the degree of memory benefit driven by memory reactivation. Finally, sleep-specific neurophysiological responses, such as spindles and slow waves, differed between the sample groups, and the spindle density during SWS predicted the degree of memory benefit observed on day 2. Taken together, these findings demonstrate that the hippocampus plays a crucial role in the consolidation of memories via covert reactivation during sleep.

A dissociation between visual and auditory hemi-inattention: Evidence from temporal order judgements

Patients with right hemisphere brain lesions often suffer from deficits in spatial attention that can be manifested in different sensory modalities. It has recently been claimed that a relationship (i.e., association) could exist between symptoms of hemi-inattention in different modalities, based on correlations between the results of visual and auditory clinical tests of neglect or extinction. However, it should be noted that the visual and auditory tasks varied greatly both in response type and level of sensitivity. Here, we have examined cross-modal associations in spatial attention deficits using a temporal order judgment task (TOJ) in which patients were required to identify which of two visual or auditory objects had appeared first. When compared to age and education matched control participants, the patients needed, on average, the contralesional stimulus to lead the ipsilesional stimulus to achieve the point of subjective simultaneity (PSS). No association between the degree of visual and auditory hemi-inattention was observed amongst the patients, suggesting that there is a certain degree of independence between the mechanisms subserving spatial attention across sensory modalities.

Correlations Between Gray Matter Reductions and Cognitive Deficits in Dementia with Lewy Bodies and Parkinson's Disease with Dementia

There is controversy regarding whether Dementia with Lewy Bodies (DLB) and Parkinsons disease with dementia (PDD) may or not be different manifestations of the same disorder. The purpose of the present study was to investigate possible correlations between brain structure and neuropsychological functions in clinically diagnosed patients with DLB and PDD. The study sample consisted of 12 consecutively referred DLB patients, 16 PDD patients, and 16 healthy control subjects recruited from an outpatient setting, who underwent MRI and neuropsychological assessment. Voxel‐based morphometry results showed that DLB patients had greater gray matter atrophy in the right superior frontal gyrus, the right premotor area and the right inferior frontal lobe compared to PDD. Furthermore, the anterior cingulate and prefrontal volume correlated with performance on the Continuous Performance Test while the right hippocampus and amygdala volume correlated with Visual Memory Test in the DLB group. In conclusion, DLB patients had more fronto‐temporal gray matter atrophy than PDD patients and these reductions correlated with neuropsychological impairment.

The organisation of nouns and verbs in bilingual speakers: A case of bilingual grammatical category-specific deficit

Abstract We report the naming performance of an early and highly proficient Catalan–Spanish bilingual woman (LPM) suffering from Alzheimers disease (AD). LPMs performance in several naming tasks revealed a disproportionate deficit for nouns in comparison to verbs. Further analyses revealed that this dissociation does not seem to be caused by damage to her semantic system, but rather by damage at the lexical level. Interestingly, the patients performance in her first and second language revealed comparable noun–verb dissociation both in terms of the magnitude of the effect and in terms of error types. These results suggest that the principles governing the organisation of lexical representations in the brain are similar for the two languages of a bilingual.

Grammatical category-specific deficits in bilingual aphasia

We report the naming performance of an early and highly proficient Spanish-Catalan bilingual (JPG) suffering from Primary Progressive Aphasia (PPA). JPGs performance revealed a grammatical category-specific deficit, with worse performance in naming verbs than nouns. This dissociation was present in oral and written naming and in his two languages, and it seems to stem from damage to, at least, the lexical level. Despite the fact that JPGs performance was qualitatively very similar across languages, his second language seemed to be more affected than his first language. These results indicate that the cortical organization of the two languages of highly proficient bilinguals follow similar organizational principles, one of this principles being grammatical class.

Improvement in GOS and GOSE scores 6 and 12 months after severe traumatic brain injury.

Primary objective: To assess improvements in Glasgow Outcome Scale (GOS) and GOS extended (GOSE) scores between 6 months and 1 year following severe traumatic brain injury (TBI). Methods and procedures: One studied 214 adult patients with severe TBI with Glasgow Coma Scale (GCS) <9 admitted to Intensive Care Unit (ICU). GOS scores were obtained 6 and 12 months after injury in 195 subjects. Patients were predominantly male (84%) and median age was 35 years. Main outcomes and results: Outcome (GOS and GOSE at 6 months and 1 year) was better in the high GCS score at admission (6–8) group than in the low score group (3–5). The improvement in GOS scores between 6 months and 1 year was greater in the high GCS score at admission group than in the low score group. At 6 months, 75 patients had died and 120 survived. None died between the 6–12-month assessments; at 12 months, 36% had improved GOS score. Conclusions: GOS scores improved between 6–12 months after severe TBI in 36% of survivors and it is concluded that the expectancy of improvement is incomplete at 6 months. This improvement was greater in patients with better GCS scores (6–8) at admission than in those with worse GCS scores (3–5).

Leftward motion restores number space in neglect

In the present study, a group of patients with left-sided neglect performed a number comparison task that co-occurred either with coherent motion in different directions or with random motion. Their performance was compared to that of a healthy control group and to a group of patients with right hemisphere damage (RHD) but no signs of neglect. The presence of leftward motion alleviated the difficulties that neglect patients typically show for a number smaller than the reference number 5 (i.e., number 4). Moreover, the standard distance effect was only present when the task co-occurred with leftward motion. These effects were not present in a group of participants with RHD without neglect or in a control group. The present data extend the effects of optokinetic stimulation (OKS) to representational neglect, suggesting that an external redirection of attention by the perception of motion may restore the altered access to the representation of the mental number line in neglect.