The Free Association Task: Proposal of a Clinical Tool for Detecting Differential Profiles of Semantic Impairment in Semantic Dementia and Alzheimer's Disease.

Backround and Objectives: It is widely agreed that patients suffering from Alzheimer's disease (AD) and patients suffering from semantic dementia (SD) might fail clinically administered semantic tasks due to a different combination of underlying cognitive deficits: namely, degraded semantic representations in SD and degraded representations plus executive control deficit in AD. However, no easy administrable test or test battery for differentiating the semantic impairment profile in these populations has been devised yet. Materials and Methods: In this study, we propose a new easy administrable task based on a free association procedure (F-Assoc) to be used in conjunction with category fluency (Cat-Fl) and letter fluency (Lett-Fl) for quantifying pure representational and pure control deficits, thus teasing apart the semantic profile of SD and AD patients. Results: In a sample of 10 AD and 10 SD subjects, matched for disease severity, we show that indices of asymmetric performance contrasting F-Assoc and each of the two verbal fluency tasks yield a clearly distinguishable discrepancy pattern across SD and AD. We also provide empirical support for the validity of an asymmetry measure contrasting F-Assoc and Cat-FL as an index of control impairment. Conclusions: The present study suggests that the free association procedure provides a pure measure of degradation of semantic representations avoiding the confound of possible concomitant executive deficits.

Semantic similarity between old and new items produces false alarms in recognition memory.

In everyday life, human beings can report memories of past events that did not occur or that occurred differently from the way they remember them because memory is an imperfect process of reconstruction and is prone to distortion and errors. In this recognition study using word stimuli, we investigated whether a specific operationalization of semantic similarity among concepts can modulate false memories while controlling for the possible effect of associative strength and word co-occurrence in an old-new recognition task. The semantic similarity value of each new concept was calculated as the mean cosine similarity between pairs of vectors representing that new concept and each old concept belonging to the same semantic category. Results showed that, compared with (new) low-similarity concepts, (new) high-similarity concepts had significantly higher probability of being falsely recognized as old, even after partialling out the effect of confounding variables, including associative relatedness and lexical co-occurrence. This finding supports the feature-based view of semantic memory, suggesting that meaning overlap and sharing of semantic features (which are greater when more similar semantic concepts are being processed) have an influence on recognition performance, resulting in more false alarms for new high-similarity concepts. We propose that the associative strength and word co-occurrence among concepts are not sufficient to explain illusory memories but is important to take into account also the effects of feature-based semantic relations, and, in particular, the semantic similarity among concepts.

Letters persistence after physical offset: visual word form area and left planum temporale. An fMRI study.

Iconic memory is a high-capacity low-duration visual memory store that allows the persistence of a visual stimulus after its offset. The categorical nature of this store has been extensively debated. This study provides functional magnetic resonance imaging evidence for brain regions underlying the persistence of postcategorical representations of visual stimuli. In a partial report paradigm, subjects matched a cued row of a 3 × 3 array of letters (postcategorical stimuli) or false fonts (precategorical stimuli) with a subsequent triplet of stimuli. The cued row was indicated by two visual flankers presented at the onset (physical stimulus readout) or after the offset of the array (iconic memory readout). The left planum temporale showed a greater modulation of the source of readout (iconic memory vs. physical stimulus) when letters were presented compared to false fonts. This is a multimodal brain region responsible for matching incoming acoustic and visual patterns with acoustic pattern templates. These findings suggest that letters persist after their physical offset in an abstract postcategorical representation. A targeted region of interest analysis revealed a similar pattern of activation in the Visual Word Form Area. These results suggest that multiple higher-order visual areas mediate iconic memory for postcategorical stimuli.

Articulatory suppression delays processing of abstract words: The role of inner speech.

Compared to concrete concepts, like "book," abstract concepts expressed by words like "justice" are more detached from sensorial experiences, even though they are also grounded in sensorial modalities. Abstract concepts lack a single object as referent and are characterised by higher variability both within and across participants. According to the Word as Social Tool (WAT) proposal, owing to their complexity, abstract concepts need to be processed with the help of inner language. Inner language can namely help participants to re-explain to themselves the meaning of the word, to keep information active in working memory, and to prepare themselves to ask information from more competent people. While previous studies have demonstrated that the mouth is involved during abstract concepts' processing, both the functional role and the mechanisms underlying this involvement still need to be clarified. We report an experiment in which participants were required to evaluate whether 78 words were abstract or concrete by pressing two different pedals. During the judgement task, they were submitted, in different blocks, to a baseline, an articulatory suppression, and a manipulation condition. In the last two conditions, they had to repeat a syllable continually and to manipulate a softball with their dominant hand. Results showed that articulatory suppression slowed down the processing of abstract more than that of concrete words. Overall results confirm the WAT proposal's hypothesis that abstract concepts processing involves the mouth motor system and specifically inner speech. We discuss the implications for current theories of conceptual representation.

Implicit prototype learning in patients with memory deficit: Evidence from a study with Alzheimer's disease patients.

OBJECTIVE: In a previous study (Zannino et al., 2012), it was demonstrated that individuals with amnestic mild cognitive impairment (MCI) were unimpaired on a new prototype learning task consisting of morphed faces (face prototype learning task [FPLT]). This paradigm was devised to improve on the classical dot pattern task by ruling out any reliance on residual episodic memory or working memory resources. In the present study, we aimed to demonstrate: first, that people with even more severe episodic memory impairment than MCI are unimpaired on a fully implicit prototype learning task and second, that the dot pattern task, at variance with the FPLT, requires a no negligible contribution from the episodic memory system. METHOD: Twenty-four persons with Alzheimer's disease (AD) and 48 healthy controls took part in this experiment. As in the original study, in addition to the FPLT, they were also administered the classical dot pattern task and an ordinary forced-choice face recognition task. RESULTS: AD performed like normal controls in the FPLT but scored significantly worse on the dot pattern task and the face recognition task. Interestingly, although performance on the face recognition task did not correlate with that on the FPLT, a significant correlation was observed between the face recognition and the dot pattern task. CONCLUSIONS: Results support both of our claims: first, that also severe amnesic people can learn new visual prototypes with a fully implicit paradigm and, second, that the classical dot pattern task requires some degree of episodic resources. Further research is needed to rule out the role of working memory in solving the FPLT. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The neural correlates of object familiarity and domain specificity in the human visual cortex: an FMRI study.

Ventral occipito-temporal cortex is known to play a major role in visual object recognition. Still unknown is whether object familiarity and semantic domain are critical factors in its functional organization. Most models assume a functional locus where exemplars of familiar categories are represented: the structural description system. On the assumption that familiarity should modulate the effect of visual noise on form recognition, we attempted to individualize the structural description system by scanning healthy subjects while they looked at familiar (living and nonliving things) and novel 3-D objects, either with increasing or decreasing visual noise. Familiarity modulated the visual noise effect (particularly when familiar items were living things), revealing a substrate for the structural description system in right occipito-temporal cortex. These regions also responded preferentially to living as compared to nonliving items. Overall, these results suggest that living items are particularly reliant on the structural description system.

Visual and semantic processing of living things and artifacts: an FMRI study.

We carried out an fMRI study with a twofold purpose: to investigate the relationship between networks dedicated to semantic and visual processing and to address the issue of whether semantic memory is subserved by a unique network or by different subsystems, according to semantic category or feature type. To achieve our goals, we administered a word-picture matching task, with within-category foils, to 15 healthy subjects during scanning. Semantic distance between the target and the foil and semantic domain of the target-foil pairs were varied orthogonally. Our results suggest that an amodal, undifferentiated network for the semantic processing of living things and artifacts is located in the anterolateral aspects of the temporal lobes; in fact, activity in this substrate was driven by semantic distance, not by semantic category. By contrast, activity in ventral occipito-temporal cortex was driven by category, not by semantic distance. We interpret the latter finding as the effect exerted by systematic differences between living things and artifacts at the level of their structural representations and possibly of their lower-level visual features. Finally, we attempt to reconcile contrasting data in the neuropsychological and functional imaging literature on semantic substrate and category specificity.

Amblyopic dyslexia: a little investigated reading disorder.

We present a case of a little investigated reading disorder we call 'amblyopic dyslexia'. The reading impairment in this patient resulted from a left extrastriate and white matter lesion causing a scotomatic area of partial deficit within the right visual field. The visual deficit was consistent with cerebral amblyopia, that is, reduced form, colour, and light sensitivity without a complete loss of vision. The patient's reading deficit was characterized by accurate single letter naming and almost accurate but effortful single word reading, with no letter-by-letter strategy. The criteria for distinguishing amblyopic dyslexia from other reading disorders and the most appropriate treatment are discussed.

Visuo-verbal distinction revisited: new insights from a study on temporal lobe epilepsy patients in the debate over the lateralization of material-specific and process-specific aspects of memory.

Introduction: The automatic interaction between a cue and a memory trace can give rise to the vivid recollection of a purely sensory past experience. But are humans able to reach back intentionally to purely sensory experiences in the absence of any exogenous or endogenous cue? In the present study, we propose an alternative hypothesis, claiming that the retrieval of associated semantic memories, stored in the left hemisphere and acting as endogenous cues, is a prerequisite for intentionally recollecting sensory experience stored in the right hemisphere during mental time travels (MTT). Methods: To investigate this issue, we administered an MTT task to 26 epileptic patients (16 males and 10 females) who had undergone right or left temporal lobectomy and to 28 age and education matched controls. The task was devised so as to require the recollection of purely visual memories in the absence of external cues. Participants also performed two conventional recognition tasks with visual and verbal materials. The three between-subjects memory tasks were analyzed separately with the Kruskal-Wallis test and the Wilcoxon rank-sum test in order to investigate differences across groups. According to our hypothesis, we expected side asymmetries in the patients' performance on the two recognition tasks but not the MTT task. Results: While patients showed the well-known hemispheric asymmetry for visual and verbal material in the (external-cue dependent) recognition tasks, no side asymmetries emerged in the purely visual MTT task. Conclusions: In keeping with the view that visual memories cannot be targeted directly by a strategic search process, the lack of any side asymmetry in our MTT task can be interpreted as a trade-off between left-sided strategic search for associated semantic memories and right-sided storage of visual ones.

The attribute priming effect in patients with Alzheimer's disease.

Experiments with semantic priming (SP) paradigms have documented early hypopriming in patients with AD when concepts are used as primes and attribute concept features as targets, suggesting that concept attributes are vulnerable to damage very early in the disease course. The aims of this study were to confirm early priming reduction in the attribute condition in patients with AD and to determine which of several semantic indexes (such as the level of distinctiveness, correlation or feature dominance of concept features) best predicts the priming effect size in AD. We administered an SP attribute condition paradigm to 20 mildly demented patients with AD and to 10 NCs. We used concept-attribute pairs for which normative data of semantic indexes relative to both concept primes (i.e., number, type, mean level of dominance, distinctiveness and correlation of features constituting the concepts) and target features (i.e., level of feature dominance, correlation and distinctiveness) were available. Results showed that compared to NCs, the AD group obtained very reduced priming facilitation. Furthermore, the item regression analyses showed that the priming decrement in the AD group was predicted by the feature dominance of the target in the related pairs; that is, the lower the target feature dominance, the lower the priming effect elicited. These results confirmed hypopriming in the attribute condition from the very early phase of AD and support the view that attributes which are more salient for the identification of a given concept are also those most resistant to semantic memory degradation in AD pathology.

Do confabulators really try to remember when they confabulate? A case report.

Since Korsakoff's (1889/1955) first descriptions of confabulation at the end of the 19th century, all attempts to understand this neuropsychological disorder have focused on memory dysfunctions. Although the precise mechanisms underlying confabulation are still a matter of debate, the prevalent view is that confabulation is the output of a faulty recollective process. In the present paper we raise doubts about this undemonstrated assumption, arguing that confabulators are not necessarily attempting to recall when they confabulate. We describe a patient (M.L.) who floridly confabulated after a ruptured aneurism of the anterior communicating artery. The patient was administered a range of verbal tasks that required either memory recollection or other kinds of cognitive processes not involving memory. We conclude that the memory dysfunction exhibited by our patient represents one of many manifestations of a more general underlying disorder characterized by an inability to select the cognitive process that matches the task requirements in conjunction with a compulsion to provide verbal responses.

Telecommunications technology in cognitive rehabilitation.

Cognitive disorders are a common long-term consequence of many forms of acquired neurological damage of different aetiology. The already high prevalence of diseases causing cognitive deficits (in particular stroke) is expected to increase in the near future, leading to a greater need for cognitive rehabilitation. The impact of cognitive impairment on daily functioning may be even greater than that of physical limitations in affected patients, contributing to the high cost of brain disorders. New technologies, including telerehabilitation, may provide an effective response to this challenge, allowing increased access to rehabilitation services as well as reduced care costs for individuals needing cognitive rehabilitation.

Category-specific naming deficit in Alzheimer's disease: the effect of a display by domain interaction.

A category-specific naming effect penalizing living things has often been reported in patients suffering from Alzheimer's disease (AD) and in other brain damaged populations, while the opposite dissociation (i.e., lower accuracy in naming nonliving than living things) is much rarer. In this study, we investigated whether the use of line drawings (rather than color photographs) in picture-naming tasks could be a relevant factor in the emergence of a category effect penalizing living things and found evidence in favor of this hypothesis. We administered the same naming tasks comprising living and nonliving items to 10 subjects suffering from AD and 10 normal controls. Once the stimuli were line drawings and once color photographs. A reliable Group x Semantic domain interaction, indicating a disproportionate impairment for living things in the AD group, was only found when line drawings were presented. Results are discussed with reference to two competing approaches to category-specificity in brain damaged people. One assumes that category effects are due to the differential involvement of dedicated neural subsystems, the other emphasizes the role of cross domains imbalances in processing demands. We conclude that our findings lead support to the latter approach.

Associative Agreement as a Predictor of Naming Ability in Alzheimer's Disease: A Case for the Semantic Nature of Associative Links.

We aimed to address the long-standing issue of the nature of the relationships that link a cue word to words associated with it. In keeping with a recently proposed neuropsychological model of semantic memory (Zannino et al., 2015), we provide support for the hypothesis that associative links are semantic in nature and not lexical. In support of this hypothesis, we demonstrate a relationship in healthy subjects between the probability of producing word X in response to cue word Y in a free association task and the probability of using word X to describe the meaning of word Y. Furthermore, we provide evidence that associative measures are altered in people suffering from Alzheimer's disease (AD) and predict their level of performance in a picture-naming task. We provide a parsimonious account of the experimental data gathered form these different sources of evidence according to the hypothesis that the links between a cue word and its associates can be viewed as binding a concept (the cue) to pieces of information regarding its meaning (the associates).

Exploring classical conditioning for strengthening the links between semantic and lexical representations in pure anomia: Preliminary findings from a single case study.

The same language symptom might arise at different functional loci in people with aphasia. Therefore, it is plausible that different therapeutic interventions should be adopted to approach the same difficulties in different patients. Although this point of view is still widely accepted, recently the focus has shifted from the functional locus of a rehabilitative intervention to the mechanisms of action underlying the relearning process. We maintain that both aspects should be taken into account when programming a rehabilitative intervention; furthermore, investigating relearning mechanisms might shed new light on the functional architecture of the disrupted processes. Here, we investigated, in a single case study, whether classical conditioning was a suitable relearning paradigm for targeting word-finding difficulties in pure anomia, that is in a patient with an impairment in accessing intact output lexical representations from a spared semantic system. Using a word-repetition task on picture presentation, we contrasted a condition in which the stimulus onset asynchrony between word and picture stimuli was well suited to produce classical conditioning with a condition in which repetition training could not benefit from this learning mechanism. Only classical conditioning training exerted a significant, long-lasting effect on our patient's naming skill. Tentative implications of our results for the functional architecture of single-word processing are discussed.

(Category-specific) semantic deficit in Alzheimer's patients: the role of semantic distance.

A semantic battery comprising items from living and nonliving categories was administered to a sample of subjects suffering from probable Alzheimer's type dementia (n=20). The results were analyzed to test the role of semantic distance in predicting group accuracy and its possible causal link with the phenomenon of a category-specific deficit for living things in the experimental population. Our findings confirm a category effect favoring nonliving items (over and above the role of confounding variables) in patients with Alzheimer's disease and support the major role of an imbalance of semantic distance in the testing material in the genesis of this phenomenon.

The role of semantic distance in category-specific impairments for living things: evidence from a case of semantic dementia.

In this paper, we describe a patient (LI) suffering from semantic dementia who showed a category-specific naming impairment for living things over and above the effects of several nonsemantic confounding variables. We investigated the characteristics of LI's impairment to address the following three issues raised in three different accounts of category-specific impairments: (i) the role of an imbalance in the loss of sensory compared to nonsensory features (assumed by the Sensory Functional Theory [Warrington, E. K., & Shallice, T. (1984). Category-specific semantic impairments. Brain, 107, 829-859]); (ii) the role of cross domain differences in Feature Correlation (assumed by the Conceptual Structure Account [Moss, H., Tyler, L. K., & Devlin, J. T. (2002). The emergence of category-specific deficits in a distributed semantic system. In: E. M. E. Forde & G. W. Humphreys (Eds.), Category Specificity in Brain and Mind (pp. 115-147). New York: Psychology Press]); (iii) the role of semantic distance (proposed by Cree and McRae [Cree, G. S., & McRae, K. (2003). Analyzing the factors underlying the structure and computation of the meaning of chipmunk, cherry, chisel, cheese, and cello (and many other such concrete nouns). Journal of Experimental Psychology: General, 132, 163-201]). We found that semantic distance was the only factor causally linked to LI's poorer performance on living things. In fact, her naming performance was less accurate on items that had many semantic neighbours, which is typical of living things. On the contrary, a feature listing task revealed that the features available to LI were not predicted by their level of correlation, as expected by the Conceptual Structure Account. Finally, at variance with the Sensory Functional Theory, although LI quoted sensory features less accurately than nonsensory ones, this did not give rise to a disproportionate loss of semantic features in the living domain.

The contribution of neurodegenerative diseases to the modelling of semantic memory: A new proposal and a review of the literature.

This paper provides a focused review of the literature on semantic impairment in semantic dementia (SD) and Alzheimer's disease (AD). An attempt is made to interpret the most relevant phenomena in the light of a new model of semantic memory. This model comprises a language-based component (disrupted in SD and AD), which supports our ability to establish reliable token vs. type relationships in the service of propositional thinking, and a philogenetically older sensorimotor component, which is needed to categorize our environment in a more implicit way. Extant neuropsychological models of semantic memory are also reviewed and compared with the new model in terms of their ability to explain the observed phenomena and to deal with the problem of establishing token vs. type relationships starting from inconsistent cross modal input representations and arbitrary category boundaries.

Category-specific impairment in patients with Alzheimer's disease as a function of disease severity: a cross-sectional investigation.

Several questions about category specificity associated with lexical-semantic deficits in Alzheimer's disease (AD) patients are still being debated. In this study, we enrolled 53 AD patients and 30 normal control subjects to investigate the following issues: Is category specificity consistently associated with AD? Do AD patients show both possible patterns of category specific impairment, i.e. selective impairment for either living things or artifacts? Is the direction of the category specific effect predictable as a function of disease severity? Is a selective impairment for living things secondary to a disproportionate loss of perceptual knowledge? We found an overall advantage for artifacts even when controlling for several confounding factors. We did not find any relation between direction of category specificity and severity of the disease or between category specificity and loss of knowledge about perceptual or functional attributes.

Intentional and automatic measures of specific-category effect in the semantic impairment of patients with Alzheimer's disease.

The breakdown of semantic knowledge relative to living and non-living categories was studied in patients with Alzheimer's disease (AD). The same living and non-living items were used in a semantic battery and in a semantic priming paradigm exploring automatic access to the semantic system. Although AD patients showed a semantic deficit on the intentional semantic battery, they demonstrated normal semantic facilitation on the priming task. In the AD group as a whole, the semantic impairment did not preferentially affect the living category either in the intentional or automatic condition. Instead, a prevalent deficit for the living category was found in three AD patients (14% of the group) on the intentional semantic tasks, but not on the automatic one. These findings support the view that the category effect may not be a generalised phenomenon in AD but may be restricted to a limited number of patients. The intentional/automatic dissociation of the semantic breakdown demonstrated by AD patients is discussed in relation to different theories regarding the organisation of semantic memory.