Dissection of the Temporofrontal Extreme Capsule Fasciculus Using Diffusion MRI Tractography and Association with Lexical Retrieval.

The well-known arcuate fasciculus that connects the posterior superior temporal region with the language production region in the ventrolateral frontal cortex constitutes the classic peri-Sylvian dorsal stream of language. A second temporofrontal white matter tract connects ventrally the anterior to intermediate lateral temporal cortex with frontal areas via the extreme capsule. This temporofrontal extreme capsule fasciculus (TFexcF) constitutes the ventral stream of language processing. The precise origin, course, and termination of this pathway has been examined in invasive tract tracing studies in macaque monkeys, but there have been no standard protocols for its reconstruction in the human brain using diffusion imaging tractography. Here we provide a protocol for the dissection of the TFexcF in vivo in the human brain using diffusion magnetic resonance imaging (MRI) tractography which provides a solid basis for exploring its functional role. A key finding of the current dissection protocol is the demonstration that the TFexcF is left hemisphere lateralized. Furthermore, using the present dissection protocol, we demonstrate that the TFexcF is related to lexical retrieval scores measured with the category fluency test, in contrast to the classical arcuate fasciculus (the dorsal language pathway) that was also dissected and was related to sentence repetition.

Age effects on the neural processing of object-context associations in briefly flashed natural scenes.

In daily life, fast visual recognition of surrounding objects is facilitated through context-based expectations. However the ability to rapidly and accurately recognize unexpected stimuli in a given environment is also crucial and this ability is impaired with age. The present fMRI study aimed at comparing in young and older adults the neural correlates of fast object processing. Patterns of cerebral activity were investigated in response to briefly-presented (100 ms) congruent and incongruent natural scenes. Participants were slower and less accurate when categorizing objects in incongruent relative to congruent contexts. This behavioral cost was notably more pronounced in the older group. Height and multivariate patterns of fMRI activity in context-selective regions were equivalent in both age groups, suggesting preserved processing of coarse scene features in older participants. Incongruent scenes elicited additional activity in the parahippocampal gyrus that possibly reflected simultaneous activation of rarely co-occurring neural representations. Contextual effects were observed in object-selective cortex for the young group only, and may be driven by detection of mismatch between actually perceived and previously-experienced associations. In the older group exclusively, increased bilateral prefrontal and left fusiform activity in response to incongruent scenes was observed. However this supplemental activity was not found to efficiently contribute to improve task performance in difficult visual conditions. Altogether these results suggest age-related changes in the interaction between object- and context-processing pathways, that may subserve impairment in fast identification of unexpected objects in natural scenes.

The repeatability of cognitive performance: a meta-analysis.

Behavioural and cognitive processes play important roles in mediating an individual's interactions with its environment. Yet, while there is a vast literature on repeatable individual differences in behaviour, relatively little is known about the repeatability of cognitive performance. To further our understanding of the evolution of cognition, we gathered 44 studies on individual performance of 25 species across six animal classes and used meta-analysis to assess whether cognitive performance is repeatable. We compared repeatability (R) in performance (1) on the same task presented at different times (temporal repeatability), and (2) on different tasks that measured the same putative cognitive ability (contextual repeatability). We also addressed whether R estimates were influenced by seven extrinsic factors (moderators): type of cognitive performance measurement, type of cognitive task, delay between tests, origin of the subjects, experimental context, taxonomic class and publication status. We found support for both temporal and contextual repeatability of cognitive performance, with mean R estimates ranging between 0.15 and 0.28. Repeatability estimates were mostly influenced by the type of cognitive performance measures and publication status. Our findings highlight the widespread occurrence of consistent inter-individual variation in cognition across a range of taxa which, like behaviour, may be associated with fitness outcomes.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

Gyrification changes are related to cognitive strengths in autism.

Background: Behavioral, cognitive and functional particularities in autism differ according to autism subgroups and might be associated with domain-specific cognitive strengths. It is unknown whether structural changes support this specialization. We investigated the link between cortical folding, its maturation and cognitive strengths in autism subgroups presenting verbal or visuo-spatial peaks of abilities. Methods: We measured gyrification, a structural index related to function, in 55 autistic participants with (AS-SOD, N = 27) or without (AS-NoSOD, N = 28) a speech onset delay (SOD) with similar symptom severity but respectively perceptual and verbal cognitive strengths, and 37 typical adolescents and young adults matched for intelligence and age. We calculated the local Gyrification Index (lGI) throughout an occipito-temporal region of interest and independently modeled age and peak of ability effects for each group. Results: Unique gyrification features in both autistic groups were detected in localized clusters. When comparing the three groups, gyrification was found lower in AS-SOD in a fusiform visual area, whereas it was higher in AS-NoSOD in a temporal language-related region. These particular areas presented age-related gyrification differences reflecting contrasting local maturation pathways in AS. As expected, peaks of ability were found in a verbal subtest for the AS-NoSOD group and in the Block Design IQ subtest for the AS-SOD group. Conclusions: Irrespective of their direction, regional gyrification differences in visual and language processing areas respectively reflect AS-SOD perceptual and AS-NoSOD language-oriented peaks. Unique regional maturation trajectories in the autistic brain may underline specific cognitive strengths, which are key variables for understanding heterogeneity in autism.

From face processing to face recognition: Comparing three different processing levels.

Verifying that a face is from a target person (e.g. finding someone in the crowd) is a critical ability of the human face processing system. Yet how fast this can be performed is unknown. The 'entry-level shift due to expertise' hypothesis suggests that - since humans are face experts - processing faces should be as fast - or even faster - at the individual than at superordinate levels. In contrast, the 'superordinate advantage' hypothesis suggests that faces are processed from coarse to fine, so that the opposite pattern should be observed. To clarify this debate, three different face processing levels were compared: (1) a superordinate face categorization level (i.e. detecting human faces among animal faces), (2) a face familiarity level (i.e. recognizing famous faces among unfamiliar ones) and (3) verifying that a face is from a target person, our condition of interest. The minimal speed at which faces can be categorized (∼260ms) or recognized as familiar (∼360ms) has largely been documented in previous studies, and thus provides boundaries to compare our condition of interest to. Twenty-seven participants were included. The recent Speed and Accuracy Boosting procedure paradigm (SAB) was used since it constrains participants to use their fastest strategy. Stimuli were presented either upright or inverted. Results revealed that verifying that a face is from a target person (minimal RT at ∼260ms) was remarkably fast but longer than the face categorization level (∼240ms) and was more sensitive to face inversion. In contrast, it was much faster than recognizing a face as familiar (∼380ms), a level severely affected by face inversion. Face recognition corresponding to finding a specific person in a crowd thus appears achievable in only a quarter of a second. In favor of the 'superordinate advantage' hypothesis or coarse-to-fine account of the face visual hierarchy, these results suggest a graded engagement of the face processing system across processing levels as reflected by the face inversion effects. Furthermore, they underline how verifying that a face is from a target person and detecting a face as familiar - both often referred to as "Face Recognition" - in fact differs.

The neural speed of familiar face recognition.

Rapidly recognizing familiar people from their faces appears critical for social interactions (e.g., to differentiate friend from foe). However, the actual speed at which the human brain can distinguish familiar from unknown faces still remains debated. In particular, it is not clear whether familiarity can be extracted from rapid face individualization or if it requires additional time consuming processing. We recorded scalp EEG activity in 28 subjects performing a go/no-go, famous/non-famous, unrepeated, face recognition task. Speed constraints were used to encourage subjects to use the earliest familiarity information available. Event related potential (ERP) analyses show that both the N170 and the N250 components were modulated by familiarity. The N170 modulation was related to behaviour: subjects presenting the strongest N170 modulation were also faster but less accurate than those who only showed weak N170 modulation. A complementary Multi-Variate Pattern Analysis (MVPA) confirmed ERP results and provided some more insights into the dynamics of face recognition as the N170 differential effect appeared to be related to a first transitory phase (transitory bump of decoding power) starting at around 140 ms, which returned to baseline afterwards. This bump of activity was henceforth followed by an increase of decoding power starting around 200 ms after stimulus onset. Overall, our results suggest that rather than a simple single-process, familiarity for faces may rely on a cascade of neural processes, including a coarse and fast stage starting at 140 ms and a more refined but slower stage occurring after 200 ms.

Comparison between PET template-based method and MRI-based method for cortical quantification of florbetapir (AV-45) uptake in vivo.

PURPOSE: Florbetapir (AV-45) has been shown to be a reliable tool for assessing in vivo amyloid load in patients with Alzheimer's disease from the early stages. However, nonspecific white matter binding has been reported in healthy subjects as well as in patients with Alzheimer's disease. To avoid this issue, cortical quantification might increase the reliability of AV-45 PET analyses. In this study, we compared two quantification methods for AV-45 binding, a classical method relying on PET template registration (route 1), and a MRI-based method (route 2) for cortical quantification. METHODS: We recruited 22 patients at the prodromal stage of Alzheimer's disease and 17 matched controls. AV-45 binding was assessed using both methods, and target-to-cerebellum mean global standard uptake values (SUVr) were obtained for each of them, together with SUVr in specific regions of interest. Quantification using the two routes was compared between the clinical groups (intragroup comparison), and between groups for each route (intergroup comparison). Discriminant analysis was performed. RESULTS: In the intragroup comparison, differences in uptake values were observed between route 1 and route 2 in both groups. In the intergroup comparison, AV-45 uptake was higher in patients than controls in all regions of interest using both methods, but the effect size of this difference was larger using route 2. In the discriminant analysis, route 2 showed a higher specificity (94.1 % versus 70.6 %), despite a lower sensitivity (77.3 % versus 86.4 %), and D-prime values were higher for route 2. CONCLUSION: These findings suggest that, although both quantification methods enabled patients at early stages of Alzheimer's disease to be well discriminated from controls, PET template-based quantification seems adequate for clinical use, while the MRI-based cortical quantification method led to greater intergroup differences and may be more suitable for use in current clinical research.

Object recognition in congruent and incongruent natural scenes: a life-span study.

Efficient processing of our complex visual environment is essential and many daily visual tasks rely on accurate and fast object recognition. It is therefore important to evaluate how object recognition performance evolves during the course of adulthood. Surprisingly, this ability has not yet been investigated in the aged population, although several neuroimaging studies have reported altered activity in high-level visual ventral regions when elderly subjects process natural stimuli. In the present study, color photographs of various objects embedded in contextual scenes were used to assess object categorization performance in 97 participants aged from 20 to 91. Objects were either animals or pieces of furniture, embedded in either congruent or incongruent contexts. In every age group, subjects showed reduced categorization performance, both in terms of accuracy and speed, when objects were seen in incongruent vs. congruent contexts. In subjects over 60 years old, object categorization was greatly slowed down when compared to young and middle-aged subjects. Moreover, subjects over 75 years old evidenced a significant decrease in categorization accuracy when objects were seen in incongruent contexts. This indicates that incongruence of the scene may be particularly disturbing in late adulthood, therefore impairing object recognition. Our results suggest that daily visual processing of complex natural environments may be less efficient with age, which might impact performance in everyday visual tasks.

Prevalence of word retrieval complaint and prediction of dementia in a population-based study of elderly subjects.

There is agreement that elderly people complain about word finding difficulties, particularly proper names. However, few studies have focused on the prevalence of this complaint in the general population, nor is it clearly known whether it is predictive of dementia. The aim of this study was to fill this gap using the PAQUID cohort. 1,838 people aged 65 or more completed questionnaires and neuropsychological evaluation regularly during 13 years. Results show that the complaint about proper name retrieval concerns 64% of people aged above 65 years, and the complaint about common names 30%. The complaint was not associated with enhanced risk of dementia, whereas short naming tests were. Only a marginal relation was found between these naming tests and word retrieval complaint. This study emphasizes the importance of proper name retrieval complaint in the general population and suggests that elderly subjects can be reassured in the absence of other symptoms.

Recognition memory and the medial temporal lobe: from monkey research to human pathology.

This review provides a historical overview of decades of research on recognition memory, the process that allows both humans and animals to tell familiar from novel items. The emphasis is put on how monkey research improved our understanding of the medial temporal lobe (MTL) role and how tasks designed for monkeys influenced research in humans. The story starts in the early 1950s. Back then, memory was not a fashionable scientific topic. It was viewed as a function of the whole brain and not of specialized brain areas. All that changed in 1957-1958 when Brenda Milner, a neuropsychologist from Montreal, described patient H.M. He forgot all events as he lived them despite a fully preserved intelligence. He had received a MTL resection to relieve epilepsy. H.M. (1926-2008) would become the most influential patient in brain science. Which structures among those included in H.M.'s large lesion were important for recognition memory could not be evaluated in humans. It was gradually understood only after the successful development of a monkey model of human amnesia by Mishkin in 1978. Selective lesions and two behavioral tasks, delayed nonmatching-to-sample and visual paired comparison, were used to distinguish the contribution of the hippocampus from that of adjacent cortical areas. Driven by findings in non-human primates, human research on recognition memory is now trying to solve the question of whether the different structures composing MTL contributes to familiarity and recollection, the two possible forms taken by recognition. We described in particular two French patients, FRG and JMG, whose deficits support the currently dominant model attributing to the perirhinal cortex a critical role in recognition memory. Research on recognition memory has implications for the clinician as it may help understanding the cognitive deficits observed in different diseases. An illustration of such approach, linking basic and applied research, is provided for Alzheimer's disease.

Neuropsychological outcome after a first symptomatic ischaemic stroke with 'good recovery'.

BACKGROUND: Neuropsychological impairment after stroke when no motor, sensory or language deficits are left remains understudied. The primary aim of this study was to assess neuropsychological outcome in a specific population of patients after a first symptomatic stroke without previous cognitive decline and with a good motor, linguistic, and functional recovery (i.e. 'good outcome'). The secondary aims were to identify the profile of this potential impairment and relations between brain lesions and neuropsychological outcome. METHODS: Sixty consecutive patients were evaluated by a comprehensive neuropsychological assessment focusing specifically on executive and attentional functions but also on memory 109 days, on average, after the infarct. Patients were compared with 40 healthy controls matched for age and education. RESULTS: Patients showed lower performance in every cognitive domain compared with controls. Along with an important executive deficit, patients were also impaired on attention and memory. Patients were not more depressed than controls, although they were more apathetic. We also found a significant positive correlation between cognitive impairment and pre-existing white matter brain lesions assessed by MRI. CONCLUSIONS: We report the first study examining the impact of a first stroke on cognition but also on psychiatric disorders in patients with good functional outcome. We found that patients considered as asymptomatic were, in fact, exhibiting a multidomain cognitive deficit that could impact return to life as before stroke.

Performance in recognition memory is correlated with entorhinal/perirhinal interictal metabolism in temporal lobe epilepsy.

In addition to the hippocampus, the entorhinal/perirhinal cortices are often involved in temporal lobe epilepsy (TLE). It has been proposed that these anterior parahippocampal structures play a key role in recognition memory. We studied the voxel-based PET correlation between number of correctly recognized targets in a new recognition memory paradigm and interictal cerebral metabolic rate for glucose, in 15 patients with TLE with hippocampal sclerosis. In comparison to healthy subjects, patients had decreased recognition of targets (P<0.001) and ipsilateral hypometabolism (relative to side of hippocampal sclerosis) of the hippocampus, entorhinal/perirhinal cortices, medial temporal pole, and middle temporal gyrus (P<0.05, corrected by false discovery rate method). Performance correlated with interictal metabolism of ipsilateral entorhinal/perirhinal cortices (P<0.005, Spearman's rank test), but this relationship was not significant in the hippocampus itself (P>0.18, Spearman's rank test). These findings highlight the preferential involvement of entorhinal/perirhinal cortices in recognition memory in patients with TLE, and suggest that recognition memory paradigms may be useful in assessing anterior parahippocampal functional status in TLE.

[Anterograde declarative memory and its models]. / La mémoire déclarative antérograde et ses modèles.

INTRODUCTION: Patient H.M.'s recent death provides the opportunity to highlight the importance of his contribution to a better understanding of the anterograde amnesic syndrome. The thorough study of this patient over five decades largely contributed to shape the unitary model of declarative memory. This model holds that declarative memory is a single system that cannot be fractionated into subcomponents. As a system, it depends mainly on medial temporal lobes structures. The objective of this review is to present the main characteristics of different modular models that have been proposed as alternatives to the unitary model. It is also an opportunity to present different patients, who, although less famous than H.M., helped make signification contribution to the field of memory. STATE OF THE ART: The characteristics of the five main modular models are presented, including the most recent one (the perceptual-mnemonic model). The differences as well as how these models converge are highlighted. PERSPECTIVES: Different possibilities that could help reconcile unitary and modular approaches are considered. CONCLUSION: Although modular models differ significantly in many aspects, all converge to the notion that memory for single items and semantic memory could be dissociated from memory for complex material and context-rich episodes. In addition, these models converge concerning the involvement of critical brain structures for these stages: Item and semantic memory, as well as familiarity, are thought to largely depend on anterior subhippocampal areas, while relational, context-rich memory and recollective experiences are thought to largely depend on the hippocampal formation.

[Isolated autobiographical amnesia: a neurological basis?]. / Amnésie autobiographique isolée : une origine neurologique ?

INTRODUCTION: The term "autobiographical memory" (AuM) refers to contextually bound experiences that occurred in a specific time, place, and affective setting. AuM is a component of memory commonly impaired in amnestic disorders. Alteration occurs rarely in isolation but rather in the setting of a larger memory impairment. Isolated AuM deficit is a controversial clinical entity, however, recently reported in the context of temporal lobe epilepsy. This study aims at characterizing this poorly documented clinical syndrome and at discussing its potential pathophysiological basis. PATIENTS AND METHODS: We studied a group of three subjects with a history of pharmacosensitive epilepsy and severe AuM complaints. They all were submitted to a neuropsychological evaluation that included an extensive episodic memory assessment, along with wake/sleep electroencephalogram (EEG) and brain magnetic resonance imaging (MRI). RESULTS: We observed the following findings: preserved autonomy and intact global cognitive functioning; normal performance to standardized episodic memory assessment, contrasting with decreased performance to specific AuM evaluation; frontal and/or temporal epileptic activity on EEG; and normal structural brain MRI. CONCLUSION: We reported on a group of patients exhibiting selective impairment of some components of personal memory, associated with interictal frontal and/or temporal abnormalities on EEG. To account for these findings, we hypothesise that interictal epileptic-related activity is impeding long-term consolidation or storage of autobiographical material.

[Pure progressive amnesia: an amnestic syndrome with preserved independence in daily life]. / L'amnésie pure progressive : un syndrome amnésique avec préservation de l'autonomie.

INTRODUCTION: Pure progressive amnesia, a form of progressive focal cortical atrophy is thought to represent the early stages of a rare form of Alzheimer's disease (AD). This syndrome is characterized by the insidious and slowly progressive breakdown of memory, in the absence of a significant impairment in other cognitive domains or in the realm of behavior. The aims of the present study were to contribute to the characterization of this poorly documented type of amnesia, to compare it with other forms of amnestic syndromes resulting from lesions to the medial temporal lobes and to discuss its potential pathophysiological basis. PATIENTS AND METHOD: We carried out three single case studies in patients presenting with pure progressive amnesia. They all underwent a neuropsychological evaluation that included an extensive assessment of spatial and recognition memory, along with brain magnetic resonance imaging and a cerebral blood flow study. RESULTS: All three patients had a severe deficit in the storage of context-free information, along with a severe visual recognition memory impairment, as previously reported in a case study on a patient with pure progressive amnesia (Cognitive Neuropsychology 23 (2006) 1230-1247). Yet, spatial memory remained well preserved, and patients maintained totally independent in everyday life. In addition, a significant atrophy of the medial temporal structures was found. DISCUSSION: This specific pattern of impairment differs from other types of amnestic syndromes after medial temporal damage and raises the question of lesional topography, as well as possible compensatory phenomena. We suggest that pure progressive amnesia results from selective damage to the ventral subhippocampal route into the hippocampal formation leading to impaired context-free memory. Spatial memory may remain intact because the dorsal parahippocampal route into the hippocampus remains functional. Pure progressive amnesia may contribute to a better understanding of the neural systems involved in declarative memory and provide a better understanding into the nature of the memory impairment that characterizes the initial stages of AD.

Alcohol disorders among Asian Americans: associations with unfair treatment, racial/ethnic discrimination, and ethnic identification (the national Latino and Asian Americans study, 2002-2003).

STUDY OBJECTIVE: To examine history of alcohol abuse/dependence disorder in relation to unfair treatment, racial/ethnic discrimination, and ethnic identification among Asian Americans. DESIGN: Weighted multivariate analyses of cross-sectional national survey data predicting lifetime history of alcohol abuse/dependence disorders. SETTING: USA, Asian Americans. PARTICIPANTS: 2007 Asian American adults recruited to the National Latino and Asian American Study (NLAAS; 2002-2003). RESULTS: Controlling for sociodemographic characteristics, Asian Americans who reported experiencing unfair treatment had higher odds of history of alcohol abuse/dependence disorder (OR 5.26, 95% CI 1.90 to 14.56). Participants who reported high levels of ethnic identification had lower odds of history of alcohol abuse/dependence disorders (OR 0.46, 95% CI 0.23 to 0.90). Ethnic identification moderated the influence of racial/ethnic discrimination (p = 0.097). Among participants with low levels of ethnic identification, racial/ethnic discrimination was associated with greater odds of having a history of alcohol disorder compared with those with high levels of ethnic identification. CONCLUSIONS: Social hazards such as unfair treatment and racial/ethnic discrimination should be considered in the development of programmes addressing alcohol disorders among Asian Americans. Interventions that promote ethnic identification in this population may be particularly relevant in mitigating the negative influence of racial/ethnic discrimination on alcohol disorders.

Profile of memory impairment and gray matter loss in amnestic mild cognitive impairment.

The present study assessed the patterns of cortical gray matter (GM) loss in patients with amnestic mild cognitive impairment (aMCI) with distinct profiles of memory impairment, i.e. aMCI patients failing on both recall and recognition memory vs. aMCI patients showing impaired recall but preserved recognition memory. This distinction is usually not taken into account in studies on aMCI and the aim of the present study was to assess whether this distinction is useful. Twenty-eight aMCI patients and 28 matched controls subjects were included. All aMCI patients failed a recall memory task (inclusion criteria). All underwent a visual recognition memory task (DMS48). However, 12 succeeded on this task while 16 failed. Relative gray matter (GM) loss was measured using voxel-based morphometry. When comparing aMCI patients to controls regardless of the profile of memory impairment, GM loss was found in temporal, parietal and frontal areas. However, in aMCI patients with preserved recognition (but impaired recall), GM loss was confined to frontal areas. This contrasted with GM loss in the right medial temporal lobe and bilateral temporo-parietal regions in aMCI patients with impaired recall and recognition memory, a pattern of GM loss usually described in early AD. We conclude that different profiles of memory impairment in aMCI patients are associated with distinct patterns of GM loss.

Identification of subgroups in amnestic mild cognitive impairment.

The DMS48 is a visual recognition memory test designed to detect memory changes in early Alzheimer disease (AD). Patients with amnestic mild cognitive impairment (aMCI) who succeeded on this task exhibited frontal hypoperfusion on SPECT. In contrast, failure was associated with temporomesial and temporoparietal hypoperfusion, a pattern usually described in the early stages of AD. It may possible to detect patients at high risk for AD within a population of aMCI.