Verbal Working Memory Impairments Research Articles

Cognitive impairment in major depressive disorder with non-suicidal self-injury: Association with the functional connectivity of frontotemporal cortex

BackgroundNon-suicidal self-injury (NSSI) may be related to serious cognitive impairment in patients with major depressive disorder (MDD), but the specific mechanism is still unclear. This study attempts to identify the neurobiological process alterations of cognitive impairment in MDD patients with NSSI by examining the functional connectivity of the frontotemporal cortex in MDD patients with or without NSSI. MethodThirty MDD patients with NSSI, 36 MDD patients without NSSI, and 35 healthy controls (HC) were included in the study. The MATRICS Consensus Cognitive Battery (MCCB) was used to comprehensively assess the cognitive function of the subjects and functional near-infrared spectroscopy (fNIRS) was used to detect the functional connectivity of the frontotemporal cortex and its brain regions of interest. ResultsMDD patients with or without NSSI had multi-domain cognitive impairments. MDD patients with NSSI showed the lowest score in performance of attention/alertness and the weakest functional connectivity of frontotemporal when compared with the MDD patients without NSSI and the HC. In addition, the functional connectivity of the bilateral frontotemporal cortex was positively correlated with verbal learning and working memory in MDD patients with NSSI. ConclusionIn MDD patients, the appearance of NSSI is often accompanied by further impairment of attention/alertness and a decline in functional connectivity of the frontotemporal cortex. The impairment of verbal learning and working memory was associated with decreased functional connectivity of the frontotemporal cortex in MDD patients with NSSI.

Effects of daytime hypercapnia on logical memory and working memory in patients with obstructive sleep apnea hypopnea syndrome

Objective: To investigate the effects of daytime hypercapnia on logical memory and working memory in patients with obstructive sleep apnea hypopnea syndrome (OSAHS). Methods: This prospective study recruited patients complaining of snoring and diagnosed with OSAHS at the Sleep Center of the Second Affiliated Hospital of Soochow University from January to November 2020. Patients were assessed clinically and scored for their memory function. All patients underwent daytime transcutaneous carbon dioxide (PtcCO2) test, and overnight polysomnography (PSG). Logical memory was scored using the Logical Memory Test (LMT), while working memory was evaluated by Digit Span Test (DST) and Cambridge Neuropsychological Test Automated Battery (CANTAB) which included Pattern Recognition Memory (PRM), Spatial Span (SSP), and Spatial Working Memory (SWM). Patients were divided into the normocapnic group and the hypercapnic group using the daytime PtcCO2 test. The clinical and PSG parameters and the memory test scores between the two groups were compared. Binary logistic stepwise regression was conducted to identify risk factors of memory impairment in OSAHS patients. Results: Among the 123 enrolled OSAHS patients, 79 were normocapnic and 44 were hypercapnic. There was no significant difference in the general clinical parameters between the two groups. The snoring history in years in the hypercapnic group was longer than that in the normocapnic group (P<0.05). Compared with the normocapnic group, the apnea-hyponea index (AHI), oxygen desaturation index (ODI) and percentage of total sleep time with oxygen saturation level<90% (TS90) of the hypercapnic group were higher (all P<0.05), while other PSG parameters exhibited no statistically significant differences. There was no statistically significant difference in the immediate logical memory and PRM immediate accuracy rate between the two groups, while the delayed logical memory, verbal and spatial working memory, and executive function were worse in the hypercapnic group, as shown by lower total LMT scores, lower DST, lower SSP scores (all P<0.05), and higher between errors and strategy scores (P<0.01) of SWM in the hypercapnic group. Binary logistic stepwise regression showed that PtcCO2 ≥45 mmHg (1 mmHg=0.133 kPa, OR=3.055, 95%CI 1.359-6.868, P=0.007) and higher body mass index (BMI) (OR=1.132, 95%CI 1.005-1.275, P=0.041) were risk factors for poor performance in Digit Span Backwards Test. Therefore, PtcCO2 ≥45 mmHg was an independent risk factors for poor performance in delayed LMT, SSP, and between errors and strategy scores in SWM (OR=3.109, 3.941, 3.238 and 2.785, respectively, all P<0.05). Conclusion: Hypercapnia had negative impacts on logical memory and working memory of OSAHS patients, especially on the delayed logical memory, verbal working memory and spatial working memory impairment.

Neurocognitive functions in persistent negative symptoms following a first episode of psychosis

Negative symptoms are present at the onset of psychosis and their persistence is significantly associated with poor psychosocial functioning and lower quality of life. Persistent negative symptoms (PNS) may be idiopathic or secondary to other factors such as depression, positive symptoms, and medication side-effects. Several studies have examined neurocognitive functions in early psychosis patients with PNS relative to non-PNS, but have not systematically controlled for secondary PNS (sPNS). The latter may have a distinct neurocognitive profile that could obscure differences between PNS and non-PNS. Using a large (n = 425) sample, we examined neurocognitive functions in PNS, sPNS, and non-PNS and hypothesized that PNS would be associated with greater impairments relative to non-PNS. Following admission to an early intervention program, a neurocognitive battery was administered after at least 3 months of treatment, and symptom data collected during a subsequent 6-month period were used to classify patients as PNS, sPNS and non-PNS. At month 12, both PNS and sPNS groups had significantly lower level of functioning relative to the non-PNS group but the sPNS group experienced higher levels of depressive and positive symptoms and were on a higher dose of antipsychotics. Relative to non-PNS, PNS patients exhibited significant impairments in verbal memory and working memory, whereas sPNS patients exhibited a trend towards greater impairments in verbal memory. This study confirms that the presence of PNS or sPNS negatively influences functioning with more selective cognitive impairments found in PNS, providing evidence that these groups of patients could benefit from different personalised interventions.

Working memory profiles of children with reading difficulties who are learning to read in Greek.

This study investigated working memory skills in a small group of 13 nine-year-old Greek children facing reading difficulties and a group of 14 age matched typical Greek readers. The children were assessed on working memory tasks measuring separately the four components of the working memory model of Baddeley and Hitch(1974) as revised by Baddeley(2000): the phonological loop, visuo-spatial sketchpad, episodic buffer and central executive. Both groups completed tests of accuracy of reading, speed of reading and text understanding. The children with reading difficulties performed significantly more poorly than typical readers on all aspects of working memory apart from visual-spatial short-term memory. These results indicate a similar verbal working memory impairment in Greek children with reading difficulties as in their English peers, despite the fact that they are learning to read a language with a transparent rather than an opaque orthography.

Does the cerebellar sequential theory explain spoken language impairments? A literature review

ABSTRACT During the past decades, converging evidence from clinical, neuroimaging and neuroanatomical studies has demonstrated the key role of the cerebellum in the processing of non-motor aspects of language. Although more is known about the way in which the cerebellum participates in the mechanisms involved in written language, there is ambiguous information on its role in other aspects of language, such as in non-motor aspects of spoken language. Thus, to contribute additional insight into this important issue, in the present work, we review several original scientific papers focusing on the most frequent non-motor spoken language impairments evidenced in patients affected by cerebellar pathology, namely, verbal working memory, grammar processing and verbal fluency impairments. Starting from the collected data, we provide a common interpretation of the spoken language disorders in cerebellar patients, suggesting that sequential processing could be the main mechanism by which the cerebellum participates in these abilities. Indeed, according to the cerebellar sequential theory, spoken language impairments could be due to altered cerebellar function to supervise, synchronize and coordinate the activity of different functional modules, affecting the correct optimization of linguistic processing.

Reduced deficits observed in children and adolescents with developmental language disorder using proper nonverbalizable span tasks

BackgroundChildren with developmental language disorder (DLD)—previously called Specific Language Impairment (SLI)—often perform poorly in verbal working memory (WM) tasks, but the picture is less clear regarding their visuospatial WM capacity. Recent research has been inconclusive regarding whether visuospatial working memory is impaired in DLD. Additionally, it is still unclear whether the putative disparity of WM performance persists in adolescence. AimsThe aim of the current study was to unveil potential impairments in verbal and visuospatial working memory in DLD by exploring two developmental age groups of French-speaking children and adolescents. MethodsThis study examined verbal and nonverbal short-term and working memory capacity using digit span and Corsi block tasks in twelve children (7–11-year-olds) and twelve adolescents (12-18-year-olds) with developmental language disorder (DLD) in comparison to that in their typically developing peers. ResultsOur findings showed that both children and adolescents with DLD have deficits in storage and processing ability for the verbal domain. However, both the short-term and working memory estimates of immediate capacity for visuospatial information in adolescents with DLD were virtually intact. ConclusionsThese results indicate that both verbal and nonverbal storage and processing capacity are largely modulated by age, suggesting that the children with DLD show virtually intact nonverbal working memory capacity as they reach adolescence.

Intervention-specific patterns of cortical function plasticity during auditory encoding in people with schizophrenia

Schizophrenia is a neurocognitive illness characterized by behavioral and neural impairments in both early auditory processing and higher order verbal working memory. Previously we have shown intervention-specific cognitive performance improvements with computerized, targeted training of auditory processing (AT) when compared to a computer games (CG) control intervention that emphasized visual processing. To investigate spatiotemporal changes in patterns of neural activity specific to the AT intervention, the current study used magnetoencephalography (MEG) imaging to derive induced high gamma band oscillations (HGO) during auditory encoding, before and after 50 h (∼10 weeks) of exposure to either the AT or CG intervention. During stimulus encoding, AT intervention-specific changes in high gamma activity occurred in left middle frontal and left middle-superior temporal cortices. In contrast, CG intervention-specific changes were observed in right medial frontal and supramarginal gyri during stimulus encoding, and in bilateral temporal cortices during response preparation. These data reveal that, in schizophrenia, intensive exposure to either training of auditory processing or exposure to visuospatial activities produces significant but complementary patterns of cortical function plasticity within a distributed fronto-temporal network. These results underscore the importance of delineating the specific neuroplastic effects of targeted behavioral interventions to ensure desired neurophysiological changes and avoid unintended consequences on neural system functioning.

Flexibility in Language Action Interaction: The Influence of Movement Type.

Recent neuropsychological studies in neurological patients and healthy subjects suggest a close functional relationship between the brain systems for language and action. Facilitation and inhibition effects of motor system activity on language processing have been demonstrated as well as causal effects in the reverse direction, from language processes on motor excitability or performance. However, as the documented effects between motor and language systems were sometimes facilitatory and sometimes inhibitory, the “sign” of these effects still remains to be explained. In a previous study, we reported a word-category-specific differential impairment of verbal working memory for concordant arm- and leg-related action words brought about by complex sequential movements of the hands and feet. In this article, we seek to determine whether the sign of the functional interaction between language and action systems of the human brain can be changed in a predictable manner by changing movement type. We here report that the sign of the effect of motor movement on action word memory can be reversed from interference to facilitation if, instead of complex movement sequences, simple repetitive movements are performed. Specifically, when engaged in finger tapping, subjects were able to remember relatively more arm-related action words (as compared to control conditions), thus documenting an enhancement of working memory brought about by simple hand movements. In contrast, when performing complex sequences of finger movements, an effector-specific degradation of action word memory was found. By manipulating the sign of the effect in accord with theory-driven predictions, these findings provide support for shared neural bases for motor movement and verbal working memory for action-related words and strengthen the argument that motor systems play a causal and functionally relevant role in language processing semantically related to action.

Load matters: neural correlates of verbal working memory in children with autism spectrum disorder

BackgroundAutism spectrum disorder (ASD) is a pervasive neurodevelopmental disorder characterised by diminished social reciprocity and communication skills and the presence of stereotyped and restricted behaviours. Executive functioning deficits, such as working memory, are associated with core ASD symptoms. Working memory allows for temporary storage and manipulation of information and relies heavily on frontal-parietal networks of the brain. There are few reports on the neural correlates of working memory in youth with ASD. The current study identified the neural systems underlying verbal working memory capacity in youth with and without ASD using functional magnetic resonance imaging (fMRI).MethodsFifty-seven youth, 27 with ASD and 30 sex- and age-matched typically developing (TD) controls (9–16 years), completed a one-back letter matching task (LMT) with four levels of difficulty (i.e. cognitive load) while fMRI data were recorded. Linear trend analyses were conducted to examine brain regions that were recruited as a function of increasing cognitive load.ResultsWe found similar behavioural performance on the LMT in terms of reaction times, but in the two higher load conditions, the ASD youth had lower accuracy than the TD group. Neural patterns of activations differed significantly between TD and ASD groups. In TD youth, areas classically used for working memory, including the lateral and medial frontal, as well as superior parietal brain regions, increased in activation with increasing task difficulty, while areas related to the default mode network (DMN) showed decreasing activation (i.e., deactivation). The youth with ASD did not appear to use this opposing cognitive processing system; they showed little recruitment of frontal and parietal regions across the load but did show similar modulation of the DMN.ConclusionsIn a working memory task, where the load was manipulated without changing executive demands, TD youth showed increasing recruitment with increasing load of the classic fronto-parietal brain areas and decreasing involvement in default mode regions. In contrast, although they modulated the default mode network, youth with ASD did not show the modulation of increasing brain activation with increasing load, suggesting that they may be unable to manage increasing verbal information. Impaired verbal working memory in ASD would interfere with the youths’ success academically and socially. Thus, determining the nature of atypical neural processing could help establish or monitor working memory interventions for ASD.

Executive dysfunction in patients with spinocerebellar ataxia type 3.

The aim of this study was to assess the cognitive functions of patients with spinocerebellar ataxia type 3(SCA3). We examined 15 patients with genetically confirmed SCA3 and 15 healthy control subjects matched for age, years of education, and intellectual ability. We administered verbal memory (word recall and word recognition) and executive function tasks (word fluency test, forward and backward digit and visual span tests, Kana Pick-out Test, Trail Making Test, and conflicting instructions and a Go/NoGo task from the Frontal Assessment Battery). We found that patients with SCA3 had significantly lower scores than the healthy control subjects on the word recall, semantic, and letter fluency, and backward digit span tests, while word recognition was well preserved. The other executive function tests showed preserved functions in the SCA3 group, indicating that visual working memory, and attention and inhibition control were not affected. The patients with SCA3 showed impaired word recall and intact word recognition, and accordingly, episodic memory encoding and storage processes in short-term memory were preserved. In category and letter-fluency tests, impairment was attributable to word-retrieval from semantic memory. Impaired verbal working memory may be involved in the retrieval of verbal information from phonological storage by means of continuous subvocal rehearsal, rather than a deficit in initial phonological encoding. Essential executive dysfunction in patients with SCA3 may be due to damage in the cerebellar cortex-ventral dentate nucleus-thalamus-prefrontal cortex circuits, which are involved in strategic retrieval of verbal information from different modes of memory storage.

Correlations between working memory impairment and neurometabolites of prefrontal cortex and lenticular nucleus in patients with major depressive disorder

BackgroundThe mechanism of working memory (WM) impairment in MDD remains unclear. We aimed to find out the mechanism by using neuropsychological tests and proton magnetic resonance spectroscopy (1H-MRS). Methods31 MDD patients and 31 healthy controls were recruited in our study. The WM performance and neurometabolite ratios of prefrontal cortex (PFC) and lenticular nucleus (LN) between two groups were evaluated and compared. And the correlations between abnormal neurometabolite ratios and WM dysfunction were computed. ResultsScores of SDMT, DST(forwards), VRS and 2-back Task(accuracy rate) in MDD were lower than HCs. NAA/Cr ratios of bilateral PFC in MDD were significantly lower than HCs, while no significant differences showed in NAA/Cr ratios of LN and Cho/Cr, mI/Cr values of the bilateral PFC and LN between two groups. And for MDD patients, NAA/Cr ratios in the right PFC were positively correlated with scores of DST (Forwards). ConclusionsOur findings suggest that depressed patients may have impairments in working memory, including phonological loop, visual-spatial sketchpad, episodic buffer and central executive. And the impairment of verbal WM and WM capacity may be associated with the abnormal neurometabolites in the right PFC.

Identifying the nature of impairments in executive functioning and working memory of children with severe difficulties in arithmetic

ABSTRACTAn age-matched achievement-matched design was used to examine whether the executive functioning and working memory impairments exhibited by children with severe difficulties in arithmetic (SDA) are better viewed as developmental lags or as cognitive deficits. Three groups of children were included: 20 SDA children, 20 typically achieving children (CM) matched in chronological age with the SDA children, and 20 younger typically achieving children (AM) matched in achievement with the SDA group. While children with SDA did not exhibit impairments in color-word inhibition and verbal working memory, they did demonstrate impairments in shifting, quantity-digits inhibition, and visuospatial working memory. As children with SDA did not perform more poorly than their AM counterparts on any of these tasks, impairments in specific areas of executive functioning and working memory appear to reflect developmental lags rather than cognitive deficits.

Effects of antidepressant therapy on neural components of verbal working memory in depression.

Impairments in verbal working memory are evident in major depression. Verbal working memory is comprised of the components of encoding, maintenance and retrieval. Whether the neural impairments are expressed in specific components, and how pharmacological therapy could modify the neural correlates are not well understood. We investigated the neural correlates of verbal working memory components in depression using the Sternberg task in a longitudinal magnetic resonance imaging study. Serial scans were acquired in 23 patients (mean age 39.8 years) during an acute depressive episode and following 12 weeks of pharmacological therapy with duloxetine and in 22 matched healthy controls (mean age 39.1 years) at the same time points. A significant group by time interaction was evident during the long maintenance phase, extending from the left middle frontal to the middle temporal and caudate regions, in which there was reduced activation in healthy participants at the follow -up scan but there were no changes in patients. Persistent neural engagement during the maintenance phase following treatment was revealed in major depression. The findings emphasize that impairments in verbal working memory may be initiated in the maintenance phase in major depression in order to sustain performance. Further research with larger sample size and using randomized, placebo-controlled double-blind studies are required to confirm our results.

The suppression effect in visuospatial and verbal working memory span tasks in patients with Alzheimer’s disease: a 2-year follow-up study

ABSTRACTThis study adapted a new task to assess visuospatial and verbal working memory impairments in patients with Alzheimer Disease (AD), including an executive strategy of information suppression. The aim was to examine the visuospatial and verbal difficulties, and additionally to explore the average sex differences, during a 2-year follow-up study. The results indicated that patients with AD showed a significantly lower performance, compared with healthy elderly controls, especially with the suppression of information required in this new task. However, suppression did not lead to a significantly greater decline in the performance of patients when compared with the control group.

Decreased processing speed might account for working memory span deficit in schizophrenia, and might mediate the associations between working memory span and clinical symptoms

Verbal working memory span is decreased in patients with schizophrenia, and this might contribute to impairment in higher cognitive functions as well as to the formation of certain clinical symptoms. Processing speed has been identified as a crucial factor in cognitive efficiency in this population. We tested the hypothesis that decreased processing speed underlies the verbal working memory deficit in patients and mediates the associations between working memory span and clinical symptoms. Forty-nine schizophrenia inpatients recruited from units for chronic and acute patients, and forty-five healthy participants, were involved in the study. Verbal working memory span was assessed by means of the letter-number span. The Digit Copy test was used to assess motor speed, and the Digit Symbol Substitution Test to assess cognitive speed. The working memory span was significantly impaired in patients (F(1,90)=4.6, P<0.05). However, the group difference was eliminated when either the motor or the cognitive speed measure was controlled (F(1,89)=0.03, P=0.86, and F(1,89)=0.03, P=0.88). In the patient group, working memory span was significantly correlated with negative symptoms (r=-0.52, P<0.0001) and thought disorganisation (r=-0.34, P<0.025) scores. Regression analyses showed that the association with negative symptoms was no longer significant when the motor speed measure was controlled (β=-0.12, P=0.20), while the association with thought disorganisation was no longer significant when the cognitive speed measure was controlled (β=-0.10, P=0.26). Decrement in motor and cognitive speed plays a significant role in both the verbal working memory impairment observed in patients and the associations between verbal working memory impairment and clinical symptoms.

Executive dysfunction in patients with temporal lobe epilepsy and its correlation with P300

To explore the changes of executive function in patients with temporal lobe epilepsy and analyze its correlation with P300 event-related potentials. Fifty patients with temporal lobe epilepsy and 30 age, gender and education-matched healthy control subjects were assessed by neuropsychological tests, including Montreal cognitive assessment (MoCA), working memory, verbal fluency, trail making, digit span, digit symbol and Stroop color-word interference to detect P300 event-related potentials. In temporal lobe epilepsy group, the scores in MoCA, verbal and non-verbal working memory, verbal fluency, digit span, digit symbol and Stroop test were lower than those of the normal control group. And trail making tests A and B became prolonged (P < 0.05). Comparing with normal control group, temporal lobe epilepsy patients had prolonged latency [(332 ± 33)ms] and decreased P300 amplitude [(10 ± 8)µV] (P < 0.05). Comparing epileptogenic focus group on the left and right sides, there was statistically significant difference in verbal working memory (P < 0.05). There was a negative correlation of P300 latency and MoCA, non-verbal working memory, digit span and digit symbol test scores (r = -0.29--0.45, P < 0.05). And a positive correlation of P300 amplitude and MoCA, non-verbal working memory, digit symbol conversion and Stroop scores was also found (r = 0.37-0.47, P < 0.05). P300 amplitude was more relevant to overall cognitive level and executive functions. Temporal lobe is involved in the regulation of executive functions. Besides a wide range of cognitive impairment, temporal lobe epilepsy patients have a number of executive dysfunctions, including working memory, cognitive flexibility, attention and inhibitory control ability. And an impairment of verbal working memory is evident in left-sided lesion. Their manifestations include decreased latency and amplitude of P300 on executive function tests. Therefore these two objective parameters may be employed to evaluate the cognitive impairment in patients with temporal lobe epilepsy.

The Development of Comorbid Conduct Problems in Children With ADHD

Objective: We describe interactions among factors that contribute to the development of conduct problems among children with ADHD. Method: An integrative developmental psychopathology analysis combines various approaches and posits one model of how diverse risk factors operate together to contribute to the development of conduct problems among children with ADHD. Results: Substantial genetic risk increases covariation between ADHD and conduct problems. Candidate genes are associated with CNS monoaminergic neurotransmission. Subsequent neurodevelopmental impairment interferes with executive function, with impaired verbal working memory playing an important role. Parent/child bi-directional influences exacerbate the risk for conduct problems when ADHD symptoms increase the likelihood of a coercive parenting style. Parent stress in reaction to child comorbid ADHD and conduct problems, and parent attribution for the child’s conduct problem behavior, add to the potential for coercion and reduce constructive parent-child interaction that might otherwise enhance the development of verbal working memory. Conclusion: In an integrated manner, these variables increase the risk that a child with ADHD will subsequently develop conduct problems.

Cognitive impairment among children at-risk for schizophrenia

Adults with schizophrenia present cognitive impairments, as do individuals at ultra-high risk for the disorder, youth with relatives with schizophrenia spectrum disorders, and children with antecedents of schizophrenia. The present study aimed to determine if impairments in childhood differed depending on the definition of risk and/or on the degree of relatedness to an affected individual, and if impairments were explained by IQ. Four groups of children aged 9–12 years were studied: (1) 13 children with ≥1 first-degree or ≥2 second-degree affected relatives (high familial loading: FHxH); (2) 14 with ≥1 affected second-degree relative (lower familial loading: FHxL); (3) 32 with well-replicated antecedents of schizophrenia (ASz); and (4) 45 typically-developing (TD) children with neither a positive family history nor antecedents. Compared to TD children, both FHxH and ASz children exhibited significantly poorer verbal comprehension, scholastic achievement, and verbal working memory, while FHxH children additionally displayed significantly lower full-scale IQ, and verbal memory and executive function impairments. After adjusting statistical analyses for IQ, group differences were attenuated. Relative to TD children, FHxL children showed no significant differences in performance. The results imply that impairments in verbal comprehension, scholastic achievement, and verbal working memory may index vulnerability for schizophrenia among children with affected relatives with the disorder and among those with multiple antecedents of the disorder who have no affected relatives. More accurate identification of children at-risk for schizophrenia and the specific deficits that they present provides opportunities for interventions such as cognitive remediation that may impact the development of the illness.

Deciphering logopenic primary progressive aphasia: a clinical, imaging and biomarker investigation

Within primary progressive aphasia the logopenic variant remains less understood than the two other main variants, namely semantic and non-fluent progressive aphasia. This may be because of the relatively small number of explored patients and because of the lack of investigations with a comprehensive three-level characterization of cognitive, brain localization and biological aspects. The aim of the present study was to decipher the logopenic variant through a multimodal approach with a large cohort of 19 patients (age 66.5 ± 8.7 years, symptom duration 3.2 ± 0.6 years) using detailed cognitive and linguistic assessments, magnetic resonance imaging and perfusion single-photon emission computed tomography as well as cerebrospinal fluid biomarkers screening for Alzheimer pathology. The linguistic assessment unveiled that language dysfunction is not limited to the typical feature of word finding and verbal working memory impairments but that it extends into the language system affecting to some degree syntactic production, phonological encoding and semantic representations. Perfusion tomography revealed damage of the temporal-parietal junction with a peak of significance in the superior temporal gyrus (Brodmann area 42), and of some less significant prefrontal areas (Brodmann areas 8, 9 and 46), whereas hippocampal cortices were unaffected. Magnetic resonance imaging, which was visually assessed in a larger group of 54 patients with logopenic, non-fluent, semantic variants as well as with posterior cortical atrophy, confirmed that the logopenic variant demonstrates predominant atrophy of left temporal-parietal junction, but that this atrophy pattern has a relatively poor sensitivity and specificity for clinical diagnosis. Finally, the biomarker study revealed that two-thirds of the logopenic patients demonstrated a profile indicative of Alzheimer pathology whereas one-third had a non-Alzheimer profile. Splitting the two groups showed that logopenic aphasia due to probable Alzheimer pathology is a more aggressive variant characterized by more extensive language/cognitive disorders affecting, in addition to lexical processes and verbal working memory, also phoneme sequencing, semantic processing and ideomotor praxis. Concordantly, logopenic aphasia due to probable Alzheimer pathology demonstrated more extensive brain hypoperfusion involving larger regions throughout the inferior parietal, the posterior-superior and the middle temporal cortex. These findings allow for unfolding logopenic aphasia into two subvariants differing by disease severity, lesion nature and lesion distribution, which has important implications for diagnosis, patient management and for potential future trials with anti-Alzheimer drugs. The present data therefore provide novel insight into the cognition and brain damage of logopenic patients while unveiling the existence of distinct diseases constituting a 'logopenic aphasia complex'.

Verbal working memory impairments following traumatic brain injury: an fNIRS investigation

The construct of working memory and its reliance on dorsolateral prefrontal cortex (DLPFC) have been the focus of many studies in healthy subjects and in clinical populations. However, transfer of knowledge gained from cognitive science studies to clinical applications can be a challenging goal. This scarce cross-dissemination may be partially due to the use of 'tools' that are limited in their ability to generate meaningful information about impairments in clinical groups. To this end, this paper investigates the use of functional near-infrared spectroscopy (fNIRS), which offers unique opportunities for recording neuroactivation. Specifically, we examine measures of the DLPFC hemodynamic response during a working memory task in adults with traumatic brain injury (TBI) and healthy controls. Analysis of hemodynamic measures showed significant differences between the two groups, even without differences in behavioral performance. Additional subtle disparities were linked to levels of performance in TBI and healthy subjects. fNIRS hemodynamic measures may therefore provide novel information to existing theories and knowledge of the working memory construct. Future studies may further define these subtle differences captured by fNIRS to help identify which components affect inter-individual variations in performance and could play a contributing role in the choice and planning of neurorehabilitation interventions targeting working memory.