Marco Calabria

Parietal rTMS distorts the mental number line: Simulating 'spatial' neglect in healthy subjects

Patients with left-sided visuospatial neglect, typically after damage to the right parietal lobe, show a systematic bias towards larger numbers when asked to bisect a numerical interval. This has been taken as further evidence for a spatial representation of numbers, perhaps akin to a mental number line with smaller numbers represented to the left and larger numbers to the right. Previously, contralateral neglect-like symptoms in physical line bisection have been induced in healthy subjects with repetitive transcranial magnetic stimulation (rTMS) over right posterior parietal lobe. Here we used rTMS over parietal and occipital sites in healthy subjects to investigate spatial representations in a number bisection task. Subjects were asked to name the midpoint of numerical intervals without calculating. On control trials subjects behaviour was similar to performance reported in physical line bisection experiments. Subjects underestimated the midpoint of the numerical interval. Repetitive transcranial magnetic stimulation produced representational neglect-like symptoms in number bisection when applied over right posterior parietal cortex (right PPC). Repetitive TMS over right PPC shifted the perceived midpoint of the numerical interval significantly to the right while occipital TMS had no effect on bisection performance. Our study therefore provides further evidence that subjects use spatial representations, perhaps akin to a mental number line, in basic numerical processing tasks. Furthermore, we showed that the right posterior parietal cortex is crucially involved in spatial representation of numbers.

Action and object naming in frontotemporal dementia, progressive supranuclear palsy, and corticobasal degeneration.

Action naming has been reported to be disproportionately impaired in comparison to object naming in patients with frontotemporal dementia (FTD). This finding has been attributed to the crucial role of frontal cortex in action naming. The investigation of object and action naming in the different subtypes of FTD, as well as in the related conditions of progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), may thus contribute to the elucidation of the cerebral correlates of the action-object discrepancy as well as provide clues to the underlying cognitive mechanisms. The results indicated that, with the exception of semantic dementia, action naming was more impaired than object naming in all patient groups. The discrepancy was similar in frontal variant of FTD and Alzheimers disease patients, whereas patients with nonfluent primary progressive aphasia, PSP, and CBD were significantly more impaired in the oral production of actions than of objects. These findings indicate that action naming impairment is not a general feature of FTD, but rather is associated with conditions that affect the frontoparietal-subcortical circuits involved in action knowledge and action representation.

Interference between number processing and line bisection: a methodology

It is usually thought that numbers are represented on a mental number line on which the progression of smaller to larger numbers occurs from left to right suggesting a spatial representation of numbers. Reciprocally, number processing has been shown to influence space representation [Fischer, M. (2001). Number processing induces spatial performance biases. Neurology, 822-826]. Specifically, it was found that when bisecting a string of numbers made up of smaller digits (1 or 2), the bisection was shifted to the left compared to bisecting a larger digit-string (8 or 9). In order to avoid any effect of physical difference in stimuli Here, we provide a simple methodology to investigate this relationship using a task involving the bisection of French number words (e.g.DEUX, NEUF). Results showed that subjects bisected strings more towards the left for smaller number words (DEUX, 2) than for larger number words (NEUF, 9), confirming that automatic number processing can influence visuo-motor aspects of behaviour. Similar results have been obtained with mirror versus canonical presentation, indicating that the reading direction is not the crucial factor of this number-induced bias. In addition, our sample of subjects showed a larger effect for number word strings than for Arabic number strings. It is therefore concluded that the implicit activation of the left/right side depends on the magnitude of the number being embedded within the stimulus lines, irrespective of its actual presentation format.

Empathy and Emotion Recognition in Semantic Dementia: A Case Report.

Recent studies have demonstrated that patients suffering from frontotemporal lobar degeneration (FTLD) show impairments in empathy and emotional processing. In this study, we examined two different aspects of these abilities in a patient with semantic dementia (SD), a variant of FTLD. The first aspect was the assessment of the cognitive and emotional components of empathy through the Interpersonal Reactivity Index. The second was the naming and comprehension of emotions using the Ekman 60 Faces Test. The patients emotion word knowledge was spared and the emotional aspects of empathy preserved. Conversely, the patient performed below average for all of the basic emotions when an emotion word had to be matched with a picture. When picture-to-picture matching was tested, however, the patient was able to recognize happiness. This case is a good example of a dissociation of covert and overt emotional functioning in SD. Results are discussed in terms of the impaired empathic behavior and emotional functioning in FTLD.

Time Perception in Spatial Neglect: A Distorted Representation?

OBJECTIVEnIt has been proposed that time, space, and numbers share the same metrics and cortical network, the right parietal cortex. Several recent investigations have demonstrated that the mental number line representation is distorted in neglect patients. The aim of this study is to investigate the relationship between time and spatial configuration in neglect patients.nnnMETHODnFourteen right-brain damaged patients (six with neglect and eight without neglect), as well as eight age-matched healthy controls, performed a time discrimination task. A standard tone (short: 700 ms and long: 1,700 ms) had to be confronted in duration to a test tone. Test tone differed of 100, 200, and 300 ms respect to the standard tone duration.nnnRESULTSnNeglect patients performed significantly worse than patients without neglect and healthy controls, irrespective of the duration of the standard tone.nnnCONCLUSIONnThese results support the hypothesis that mental representations of space and time both share, to some extent, a common cortical network. Besides, spatial neglect seems to distort the time representation, inducing an overestimation of time durations.

Efficacy of acetyl-cholinesterase-inhibitor (ACHEI) treatment in Alzheimer's disease: A 21-month follow-up ''real world'' study

Long-term efficacy of acetyl-cholinesterase-inhibitor (ACHEI) treatment in mild-to-moderate Alzheimers disease (AD) is of great relevance for clinical routine and has been investigated over a 21-month period of treatment in a real word population. We investigated cognitive (mini mental state examination=MMSE) and functional (instrumental activities of daily living=IADL; activities of daily living=ADL) outcomes in 427 AD patients throughout the above period. At the end of the study, first-time drug takers (naives) declined by 1.2 MMSE points, whereas non-naives by 3.8 points. Predictors of responsiveness for first-time drug takers were MMSE score at baseline and MMSE points gained at 3 months of treatment. Further investigations are needed to shed light on the characteristics of responsiveness to a tailored ACHEI treatment for dementia.

Face–name repetition priming in semantic dementia: A case report

Repetition priming (RP) has been employed as a measure of implicit processing in patients suffering from a breakdown of semantic memory, as in the case of semantic dementia (SD), a subtype of frontotemporal lobar degeneration (FTLD). Here, we investigated face-name representation in a case of SD using a paradigm of within- and cross-domain repetition priming. Compared to ten healthy participants, SD patient did not show any facilitation when a famous name was primed by its own face (cross-domain) or when the prime was the same proper name (within-domain). Results are discussed within the hypothesis of a degradation of face and name representation, one of the most consistent accounts explaining semantic deficits in SD.