The Semantic Association Test (SAT): normative data from healthy Italian participants and a validation study in aphasic patients.

The Semantic Association Test assesses several aspects of Semantic Memory (Categorical, Encyclopedic, Functional, and Visual Encyclopedic associations: CAs, EAs, FAs and VEAs), using a picture-to-picture matching paradigm. Normative data were collected from a group of 329 healthy participants (178 females) with mean 51.1 (range 20-90) years of age and mean 11.89 (range 5-19) years of education. Raw scores of healthy participants, pre-calculated correction factors for age and educational level, and Equivalent Scores are provided. The SAT was validated in a sample of 139 left brain-damaged persons with aphasia (PWA). Both groups (healthy participants and PWA) scored worse in the CA and EA conditions. The performance of the PWA group was overall defective, and global aphasics scored worse than persons with other types of aphasia. However, several PWA did not show impairments in the SAT. Dissociations were also found, with individual PWA showing defective performance confined to a single category. These results present the SAT as a tool that is useful to detect impairments of visual Semantic Memory, providing normative data from healthy participants and a validation study in PWA.

White matter networks dissociate semantic control from semantic knowledge representations: Evidence from voxel-based lesion-symptom mapping.

Although semantic system is composed of two distinctive processes (i.e., semantic knowledge and semantic control), it remains unknown in which way these two processes dissociate from each other. Investigating the white matter neuroanatomy underlying these processes helps improve understanding of this question. To address this issue, we recruited brain-damaged patients with semantic dementia (SD) and semantic aphasia (SA), who had selective predominant deficits in semantic knowledge and semantic control, respectively. We built regression models to identify the white matter network associated with the semantic performance of each patient group. Semantic knowledge deficits in the SD patients were associated with damage to the left medial temporal network, while semantic control deficits in the SA patients were associated with damage to the other two networks (left frontal-temporal/occipital and frontal-subcortical networks). The further voxel-based analysis revealed additional semantic-relevant white matter tracts. These findings specify different processing principles of the components in semantic system.

Gerstmann Syndrome.

PURPOSE OF REVIEW: Gerstmann (left angular gyrus) syndrome includes the tetrad of finger agnosia (inability to distinguish, name, and recognize the fingers), agraphia (acquired disturbance in the ability to write), acalculia (loss of the ability to perform arithmetical operations and use numerical concepts), and right-left disorientation (right-left discrimination defect when using language). There is some disagreement regarding its exact localization, but it most likely involves the left angular gyrus with a probable subcortical extension. This article reviews recent research on the clinical aspects of this syndrome. RECENT FINDINGS: During the last years, just some few new reports of Gerstmann syndrome are found in neurological and neuropsychological literature. Most of the reports are single-case reports. An association between Gerstmann syndrome and the so-called semantic aphasia has been pointed out. Two different explanations to this unusual syndrome have been recently proposed: (1) the pathological process is located in the left parietal white matter disconnecting separate cortical networks and (2) it represents a disturbance in the ability to verbally mediate some spatial knowledge. Although Gerstmann syndrome continues as a controversial syndrome, and most of the reports are single case reports, recently two different explanations have been advance the understanding of this polemic but fascinating syndrome.

Divergent effects of healthy ageing on semantic knowledge and control: Evidence from novel comparisons with semantically impaired patients.

Effective use of semantic knowledge requires a set of conceptual representations and control processes which ensure that currently relevant aspects of this knowledge are retrieved and selected. It is well-established that levels of semantic knowledge increase across the lifespan. However, the effects of ageing on semantic control processes have not been assessed. I addressed this issue by comparing the performance profiles of young and older people on a verbal comprehension test. Two sets of variables were used to predict accuracy and RT in each group: (1) the psycholinguistic properties of words probed in each trial and (2) the performance on each trial by two groups of semantically impaired neuropsychological patients. Young people demonstrated poor performance for low-frequency and abstract words, suggesting that they had difficulty processing words with intrinsically weak semantic representations. Indeed, performance in this group was strongly predicted by the performance of patients with semantic dementia, who suffer from degradation of semantic knowledge. In contrast, older adults performed poorly on trials where the target semantic relationship was weak and distractor relationships strong - conditions which require high levels of controlled processing. Their performance was not predicted by the performance of semantic dementia patients, but was predicted by the performance of patients with semantic control deficits. These findings indicate that the effects of ageing on semantic cognition are more complex than has previously been assumed. While older people have larger stores of knowledge than young people, they appear to be less skilled at exercising control over the activation of this knowledge.

Toward a functional neuroanatomy of semantic aphasia: A history and ten new cases.

Almost 70 years ago, Alexander Luria incorporated semantic aphasia among his aphasia classifications by demonstrating that deficits in linking the logical relationships of words in a sentence could co-occur with non-linguistic disorders of calculation, spatial gnosis and praxis deficits. In line with his comprehensive approach to the assessment of language and other cognitive functions, he argued that deficits in understanding semantically reversible sentences and prepositional phrases, for example, were in line with a single neuropsychological factor of impaired spatial analysis and synthesis, since understanding such grammatical relationships would also draw on their spatial relationships. Critically, Luria demonstrated the neural underpinnings of this syndrome with the critical implication of the cortex of the left temporal-parietal-occipital (TPO) junction. In this study, we report neuropsychological and lesion profiles of 10 new cases of semantic aphasia. Modern neuroimaging techniques provide support for the relevance of the left TPO area for semantic aphasia, but also extend Luria's neuroanatomical model by taking into account white matter pathways. Our findings suggest that tracts with parietal connectivity - the arcuate fasciculus (long and posterior segments), the inferior fronto-occipital fasciculus, the inferior longitudinal fasciculus, the superior longitudinal fasciculus II and III, and the corpus callosum - are implicated in the linguistic and non-linguistic deficits of patients with semantic aphasia.

The meaning of 'life' and other abstract words: Insights from neuropsychology.

There are a number of long-standing theories on how the cognitive processing of abstract words, like 'life', differs from that of concrete words, like 'knife'. This review considers current perspectives on this debate, focusing particularly on insights obtained from patients with language disorders and integrating these with evidence from functional neuroimaging studies. The evidence supports three distinct and mutually compatible hypotheses. (1) Concrete and abstract words differ in their representational substrates, with concrete words depending particularly on sensory experiences and abstract words on linguistic, emotional, and magnitude-based information. Differential dependence on visual versus verbal experience is supported by the evidence for graded specialization in the anterior temporal lobes for concrete versus abstract words. In addition, concrete words have richer representations, in line with better processing of these words in most aphasic patients and, in particular, patients with semantic dementia. (2) Abstract words place greater demands on executive regulation processes because they have variable meanings that change with context. This theory explains abstract word impairments in patients with semantic-executive deficits and is supported by neuroimaging studies showing greater response to abstract words in inferior prefrontal cortex. (3) The relationships between concrete words are governed primarily by conceptual similarity, while those of abstract words depend on association to a greater degree. This theory, based primarily on interference and priming effects in aphasic patients, is the most recent to emerge and the least well understood. I present analyses indicating that patterns of lexical co-occurrence may be important in understanding these effects.

Semantic memory: Which side are you on?

We present two patients in whom the combination of lesion site and cognitive performance was uniquely informative about the organisation and functional anatomy of semantic memory. One had had a single lobar stroke with an unusual distribution, largely destroying the whole of the left temporal lobe ventral to the superior temporal sulcus. The other patient had had herpes simplex encephalitis with destruction that was confined to the left cerebral hemisphere. The lesion again mainly encompassed the left temporal lobe, but also extended to the left inferior frontal gyrus. Cognitive outcomes in the two patients were compared with each other and with published results from patients with semantic dementia. This is because, whereas the majority of semantic dementia patients present with more prominent atrophy of the left rostroventral temporal lobe, they invariably have a degree of atrophy in the mirror region on the right that progresses. Semantic dementia therefore provides no clear evidence about the specific role of the left rostroventral temporal lobe. The two patients showed a highly consistent cognitive profile. Their deficits were also similar in many respects to that observed in patients with mild-moderate semantic dementia, including severe anomia that was not resolved by phonological cues and impairment on non-verbal as well as verbal semantic tasks. Certain key features of the semantic dementia profile, however-including sensitivity to the familiarity and typicality of the stimulus materials-appeared only in tasks requiring verbal output in these two patients with unilateral left temporal lesions. Results in these cases provide some of the first definitive evidence regarding the specific functions of the left anterior temporal lobe.

Deregulated semantic cognition contributes to object-use deficits in Alzheimer's disease: A comparison with semantic aphasia and semantic dementia.

Executive control is impaired from the early stages of Alzheimer's Disease (AD) and this produces deregulated semantic cognition (Corbett, Jefferies, Burns, & Lambon Ralph, ; Perry, Watson, & Hodges, ). While control deficits should affect semantic retrieval across all modalities, previous studies have typically focused on verbal semantic tasks. Even when non-verbal semantic tasks have been used, these have typically employed simple picture-matching tasks, which may be influenced by abnormalities in covert naming. Therefore, in the present study, we examined 10 patients with AD on a battery of object-use tasks, in order to advance our understanding of the origins of non-verbal semantic deficits in this population. The AD patients' deficits were contrasted with previously published performance on the same tasks within two additional groups of patients, displaying either semantic degradation (semantic dementia) or deregulation of semantic retrieval (semantic aphasia; Corbett, Jefferies, Ehsan, & Lambon Ralph, ). While overall accuracy was comparable to the scores in both other groups, the AD patients' object-use impairment most closely resembled that observed in SA; they exhibited poorer performance on comprehension tasks that placed strong demands on executive control. A similar pattern was observed in the expressive domain: the AD and SA groups were relatively good at straightforward object use compared to executively demanding, mechanical puzzles. Error types also differed: while all patients omitted essential actions, the SA and AD groups' demonstrations also featured unrelated intrusions. An association between AD patients' object use and their scores on standard executive measures suggested that control deficits contributed to their non-verbal semantic deficits. Moreover, in a task specifically designed to manipulate executive demand, patients with AD (and SA) exhibited difficulty in thinking flexibly about the non-canonical uses of everyday objects, especially when distracted by semantically related objects. This study provides converging evidence for the notion that a failure of regulatory control contributes to multimodal semantic impairment in AD and uniquely demonstrates this pattern for the highly non-verbal domain of object use.

On the origins of calculation abilities.

A historical review of calculation abilities is presented. Counting, starting with finger sequencing, has been observed in different ancient and contemporary cultures, whereas number representation and arithmetic abilities are found only during the last 5000-6000 years. The rationale for selecting a base of ten in most numerical systems and the clinical association between acalculia and finger agnosia are analyzed. Finger agnosia (as a restricted form of autotopagnosia), right-left discrimination disturbances, semantic aphasia, and acalculia are proposed to comprise a single neuropsychological syndrome associated with left angular gyrus damage. A classification of calculation disturbances resulting from brain damage is presented. It is emphasized that using historical/anthropological analysis, it becomes evident that acalculia, finger agnosia, and disorders in right-left discrimination (as in general, in the use of spatial concepts) must constitute a single clinical syndrome, resulting from the disruption of some common brain activity and the impairment of common cognitive mechanisms.

A proposed reinterpretation of Gerstmann's syndrome.

Gerstmann's syndrome includes the clinical tetrad of finger agnosia, agraphia, acalculia, and right-left confusion. Some disagreement remains with regard to the exact localization of the syndrome, but most probable it involves the left angular gyrus with a subcortical extension. Several authors have suggested that a defect in mental spatial rotations could simultaneously account for acalculia, right-left disorientation, and finger agnosia. It has been also suggested that semantic aphasia is always associated with acalculia; as a matter of fact, left angular gyrus has a significant involvement in semantic processing. In this paper, it is proposed that Gerstmann's syndrome should include: acalculia, finger agnosia, right-left disorientation, and semantic aphasia, but not agraphia. When the pathology extends toward the superior parietal gyrus, agraphia can be found. A fundamental defect (i.e., an impairment in verbally mediated spatial operations) could explain these apparently unrelated clinical signs.

Afasia logopénica: presentación de un caso y revisión de la literatura / Logopenic Aphasia: a case report an review of the literature

With the progressive aging of the Chilean population the diagnosis of neurodegenerative disorders is increasingly common, and among them is Primary Progressive Aphasia (PPA), with specific symptoms but late consultation. PPA is a clinical syndrome characterized by the degeneration of language regions in the dominant hemisphere that determines an insidious and progressive loss of language. Two types of PPA were recognized: Progressive non-fluent Aphasia (APnF) and Progressive Semantic Aphasia (DS), and was recently identified as a new type, Logopénica Progressive Aphasia (APL). We describe a case evaluated at the University of Chile Clinical Hospital of a woman of 54 years who have a history of 2-3 years of fluent speech with reduced speed due to the difficulty in finding words, had shortcomings in repetition of complex words, phrases and sentences, presence of phonemic paraphasias and impaired episodic memory. What in the phonological assessment supports a diagnosis of APL. Despite the above, the neurological examination was normal. The APL has been associated with Alzheimer's disease because it presents impaired episodic memory and the neuropathological changes most frequently encountered are amyloid plaques and neurofibrillary tangles. Through this article you may learn more about this disease and who to go if you or some colleague have symptoms to receive some guidance.

Con el progresivo envejecimiento de la población Chilena el diagnóstico de enfermedades neurodegenerativas es cada vez más com ún, y entre ellas está la afasia progresiva primaria (PPA), de síntomas específicos pero consulta tardía. PPA es un síndrome clínico caracterizado por la degeneración de las regiones del lenguaje en el hemisferio dominante que determina una pérdida insidiosa y progresiva del lenguaje. Fueron reconocidos dos tipos de PPA: Afasia Progresiva no fluente (APnF) y Afasia Progresiva Semántica (DS), y recientemente fue identificado un nuevo tipo como, Afasia Progresiva Logopénica (APL). Se describe un caso evaluado en el Hospital Clínico Universidad de Chile de una mujer de 54 años que presenta una historia de 2-3 años de habla fluida, con disminución de la velocidad debido a la dificultad para encontrar palabras, presentaba fallas en repetición de palabras complejas, frases y oraciones, presencia de parafasias fonémicas y problemas de memoria episódica. Lo que en la evaluación fonológica es compatible con un diagnóstico de APL. A pesar de todo lo anterior el examen neurológico fue normal. La APL se ha asociado con la enfermedad de Alzheimer, ya que presenta deterioro de la memoria episódica y los cambios neuropatológicos más frecuentes son las placas amiloides y los ovillos neurofibrilares. A través de este artículo podrán conocer más acerca de esta enfermedad y a quien acudir en caso de presentar síntomas usted o algún conocido para recibir alguna orientación.