Neuroticism is associated with increase in depression symptoms over time in older adults with type 2 diabetes.

OBJECTIVES: The likelihood of depression symptoms in those with type 2 diabetes (T2D) is high. Psychological risk factors enhancing comorbidity of depression symptoms in T2D are yet to be determined. The present study examines the cross-sectional and longitudinal relationship between personality traits and distinct depression dimensions in older adults with T2D. METHODS: Participants were older adults (age ≥65yeas) with T2D from the Israel Diabetes and Cognitive Decline (IDCD) study (N = 356), with complete data on depression [Geriatric Depression Scale (GDS) - 15 item version] and its dimensions- namely, dysphoric mood, apathy, hopelessness, memory complains and anxiety, and on personality [Big Five Inventory (BFI)]. Logistic and mixed linear regression models examined cross-sectional and longitudinal associations while adjusting for socio-demographics, cognition, cardiovascular and diabetes-related factors. RESULTS: Cross-sectionally, high neuroticism was associated with high scores in total GDS and in all depression-dimensions, except memory complaints. Higher extroversion was associated with lower total GDS and with lower scores on all depression dimensions, except anxiety. High levels of neuroticism were associated with increase in total number of depression symptoms over time. CONCLUSIONS: In older adults with T2D, neuroticism and extroversion are associated with most depression dimensions suggesting that these traits relate to a global depression symptomatology rather than to any specific dimension or phenomenology. High neuroticism was associated with increase in depression symptoms over time, highlighting its role in the development of depression symptoms in older adults with T2D.

Gyrification in relation to cortical thickness in the congenitally blind.

Greater cortical gyrification (GY) is linked with enhanced cognitive abilities and is also negatively related to cortical thickness (CT). Individuals who are congenitally blind (CB) exhibits remarkable functional brain plasticity which enables them to perform certain non-visual and cognitive tasks with supranormal abilities. For instance, extensive training using touch and audition enables CB people to develop impressive skills and there is evidence linking these skills to cross-modal activations of primary visual areas. There is a cascade of anatomical, morphometric and functional-connectivity changes in non-visual structures, volumetric reductions in several components of the visual system, and CT is also increased in CB. No study to date has explored GY changes in this population, and no study has explored how variations in CT are related to GY changes in CB. T1-weighted 3D structural magnetic resonance imaging scans were acquired to examine the effects of congenital visual deprivation in cortical structures in a healthy sample of 11 CB individuals (6 male) and 16 age-matched sighted controls (SC) (10 male). In this report, we show for the first time an increase in GY in several brain areas of CB individuals compared to SC, and a negative relationship between GY and CT in the CB brain in several different cortical areas. We discuss the implications of our findings and the contributions of developmental factors and synaptogenesis to the relationship between CT and GY in CB individuals compared to SC. F.

Choices of (in)action in obesity: Implications for research on treatment and prevention.

The obesity epidemic has crossed social-demographic barriers and is a matter of significant concern. Why do individuals fail to restrain from eating high-calorie foods and fail to follow treatment routines that reduce the risk of health complications? These questions have been addressed through behavioral and brain imaging studies on prefrontal cortex inhibitory mechanisms. Failure to inhibit undesirable behaviors has become a hallmark of obesity. In many life situations, obesity risk is increased by inaction (e.g., not taking blood pressure medication, not following a healthy diet). Risk by inaction has been defined as passive risk-taking, and it is correlated with traits such as procrastination, future time perspective, and cognitive avoidance. To the present, passive tendencies, specifically in the context of risk-taking behaviors, have not been addressed in the obesity literature. We introduce a framework in which active and passive risk-taking behaviors are integrated within the scope of bidirectional models of obesity that describe the brain as both the cause and the consequence of obesity vulnerability. The present perspective aims to foster new research on treatment and prevention, and also on the neurobiology of passive behaviors in obesity and other metabolic conditions.

Cognitive and brain correlates of acquired number-colour synaesthetic-like associations.

Synaesthesia is a condition in which one sensory dimension triggers another sensation. The exact contribution of genetic and environmental factors in synaesthesia is not yet fully understood. Most synaesthesia phenotypes involve associations in which the synaesthetic inducer constitutes some form of linguistic/conceptual information acquired during the course of development (e.g., digits, letters, and names of months). To study the role of learning in synaesthesia, we induced synaesthesia by training and examined the behavioural and brain correlates of number-colour associations. We took advantage of the well-known behavioural and neural signature of numbers and used number symbols as inducers. Short (2 weeks) and long (4 weeks) training protocols were conducted with two different groups. Task-related BOLD response was acquired while participants performed Stroop tasks requiring naming colours while ignoring the stimuli (i.e., number symbols, dots, words). If the arbitrary association involving number-colour is automatic, the irrelevant dimension (i.e., numbers) would interfere with the colour response. In addition, if number-colour associations are transferred to linguistic and non-symbolic representations, the passive viewing of stimuli (i.e., words and dots) would disrupt colour naming. Behavioural findings showed automatic associations as both training protocols elicited reliable congruency effects for all stimulus dimensions. Congruency effects following both training protocols produced reliable brain activations in various cortical sites involved in number and in cognitive control. The behavioural and brain patterns reported here support the role of learning in the brain correlates of developmental synaesthesia and provide the first evidence that automatic associations involving different magnitude dimensions can be acquired.

Control of response interference: caudate nucleus contributes to selective inhibition.

While the role of cortical regions in cognitive control processes is well accepted, the contribution of subcortical structures (e.g., the striatum), especially to the control of response interference, remains controversial. Therefore, the present study aimed to investigate the cortical and particularly subcortical neural mechanisms of response interference control (including selective inhibition). Thirteen healthy young participants underwent event-related functional magnetic resonance imaging while performing a unimanual version of the Simon task. In this task, successful performance required the resolution of stimulus-response conflicts in incongruent trials by selectively inhibiting interfering response tendencies. The behavioral results show an asymmetrical Simon effect that was more pronounced in the contralateral hemifield. Contrasting incongruent trials with congruent trials (i.e., the overall Simon effect) significantly activated clusters in the right anterior cingulate cortex, the right posterior insula, and the caudate nucleus bilaterally. Furthermore, a region of interest analysis based on previous patient studies revealed that activation in the bilateral caudate nucleus significantly co-varied with a parameter of selective inhibition derived from distributional analyses of response times. Our results corroborate the notion that the cognitive control of response interference is supported by a fronto-striatal circuitry, with a functional contribution of the caudate nucleus to the selective inhibition of interfering response tendencies.

Space counts! Brain correlates of spatial and numerical representations in synaesthesia.

Over-learned semantic representations, such as numbers, are strongly associated with space in normal cognition, and in the phenomenon called number-space synaesthesia. In number-space synaesthesia, numbers are linked to spatial locations in an idiosyncratic way. Synaesthetes report numbers as belonging to a specific location, or feelings that a specific location is the right location for that number. What does really differentiate synaesthetes from non-synaesthetes with respect to their number-space representation? Here we present a number-space synaesthete, MkM, whose number-space representation dramatically differs from that of controls. We examined the impact of spatial distance with respect to MkM's mental number line (MNL), and numerical distance with respect to the conceptualized horizontal representation of numbers. In a behavioural experiment, MkM and controls performed number comparison tasks in which they reported either the larger numerical value (number task) or the larger stimulus (physical task) (Experiment 1). A spatial distance effect was found only for MkM. In a brain imaging experiment, MkM and controls compared a single presented digit with an internal reference (Experiment 2). Consistent with the behavioural results, spatial distance elicited significant brain activations only for MkM in different cortical sites including the left supramarginal gyrus. Numerical distance elicited significant brain activations only for controls in the left somatosensory cortex and in the right operculum. We propose that two types of representation are accessed in synaesthesia: one derived by the semantic coding of numbers across space (described by the MNL), and an explicit spatial representation derived from the position of number within the synaesthetic association. The level of overlap between these two forms of representation depends on the shape of the synaesthetic number-space association.

Preserved but Less Efficient Control of Response Interference After Unilateral Lesions of the Striatum.

Previous research on the neural basis of cognitive control processes has mainly focused on cortical areas, while the role of subcortical structures in cognitive control is less clear. Models of basal ganglia function as well as clinical studies in neurodegenerative diseases suggest that the striatum (putamen and caudate nucleus) modulates the inhibition of interfering responses and thereby contributes to an important aspect of cognitive control, namely response interference control. To further investigate the putative role of the striatum in the control of response interference, 23 patients with stroke-induced lesions of the striatum and 32 age-matched neurologically healthy controls performed a unimanual version of the Simon task. In the Simon task, the correspondence between stimulus location and response location is manipulated so that control over response interference can be inferred from the reaction time costs in incongruent trials. Results showed that stroke patients responded overall slower and more erroneous than controls. The difference in response times (RTs) between incongruent and congruent trials (known as the Simon effect) was smaller in the ipsilesional/-lateral hemifield, but did not differ significantly between groups. However, in contrast to controls, stroke patients exhibited an abnormally stable Simon effect across the reaction time distribution indicating a reduced efficiency of the inhibition process. Thus, in stroke patients unilateral lesions of the striatum did not significantly impair the general ability to control response interference, but led to less efficient selective inhibition of interfering responses.

Tactile enumeration: A case study of acalculia.

Enumeration is one of the building blocks of arithmetic and fingers are used as a counting tool in early steps. Subitizing-fast and accurate enumeration of small quantities-has been vastly studied in the visual modality, but less in the tactile modality. We explored tactile enumeration using fingers, and gray matter (GM) changes using voxel-based morphometry (VBM), in acalculia. We examined JD, a 22-year-old female with acalculia following a stroke to the left inferior parietal cortex. JD and a neurologically healthy normal comparison (NC) group reported how many fingers were stimulated. JD was tested at several time points, including at acute and chronic phases. Using the sensory intact hand for tactile enumeration, JD showed deficit in the acute phase, compared to the NC group, and improvement in the chronic phase of (1) the RT slope of enumerating up to four stimuli, (2) enumerating neighboring fingers, and (3) arithmetic fluency performance. Moreover, VBM analysis showed a larger GM volume for JD relative to the NC group in the right middle occipital cortex, most profoundly in the chronic phase. JD's performance serves as a first glance of tactile enumeration in acalculia. Pattern-recognition-based results support the suggestion of subitizing being the enumeration process when using one hand. Moreover, the increase in GM in the occipital cortex lays the groundwork for studying the innate and primitive ability to perceive and evaluate sizes or amounts-"sense of magnitude"- as a multisensory magnitude area and as part of a recovery path for deficits in basic numerical abilities.

Neuroanatomical basis of number synaesthesias: A voxel-based morphometry study.

In synaesthesia, a specific sensory dimension leads to an involuntary sensation in another sensory dimension not commonly associated with it; for example, synaesthetes may experience a specific colour when listening or thinking of numbers or letters. Large-scale behavioural studies provide a rich description of different synaesthesia phenotypes, and a great amount of research has been oriented to uncovering whether a single or multiple brain mechanisms underlie these various synaesthesia phenotypes. Interestingly, most of the synaesthetic inducers are conceptual stimuli such as numbers, letters, and months. However, the impact of these concepts on the synaesthetic brain remains largely unexplored. Numbers appear as the most typical inducer in two common types of synaesthesia: grapheme-colour and sequence-space. Numbers are symbols that denote quantity information and their processing recruits a specific neural network. Therefore, numbers may play an important role in the brain mechanisms underlying some types of synaesthesia. We used voxel-based morphometry (VBM) to compare grey matter (GM) volume in synaesthetes and controls. Relative to controls, synaesthetes showed increase in GM in the right amygdala and in the left cerebellum. Within the synaestheste group, comparing synaesthetes who reported numbers as the inducer with synaesthetes who reported other stimuli as the inducer revealed increase in GM in the left angular gyrus, which is associated with the verbal aspect of number processing. These results reveal neuroanatomical differences between synaesthetes and controls, and show the impact of the type of inducer in the synaesthetic brain. We discuss these findings in line with current neurobiological models of synaesthesia.

What Can Illusory Conjunctions Reveal About Synaesthetic Bindings?

The visual system successfully binds the shapes and colours of objects; therefore, our visual experience regarding the objects around us is coherent. However, this binding process can break down when attention is diverted, producing illusory conjunctions (ICs); for example, when presented with a red 2 and a green 5, the observer may report a green 2 and a red 5. The strongest observation of binding in human cognition is found in synaesthesia. In grapheme-colour synaesthesia, linguistic stimuli (e.g., letters or numbers) are strongly associated with colours. It is debatable whether these highly stable bindings constitute a form of early binding that occurs outside the focus of attention. We examined for the first time the occurrence of ICs in grapheme-colour synaesthesia. Experiment 1 replicated our previous finding, showing the effects of numerical distance on ICs (Arend et al., Psychon. Bull. Rev. 2013, 20, 1181-1186). Participants viewed a display containing two centrally presented letters and two coloured numbers and were asked to report: (1) whether the letters were same/different, (2) the colour of the larger number, and (3) the level of confidence concerning the colour of the number. Experiment 2 used a modified version of this task. Synaesthetes (N=5) and controls (N=15) viewed number-colour pairs that were congruent or incongruent with that of the synaesthetic association. Grapheme-colour synaesthesia significantly affected ICs on incongruent but not on congruent trials. Our findings strongly support the notion that shape and colour are free-floating features in synaesthesia, similar to what is observed in normal cognition.

Automatic numerical-spatial association in synaesthesia: An fMRI investigation.

A horizontal mental number line (MNL) is used to describe how quantities are represented across space. In humans, the neural correlates associated with such a representation are found in different areas of the posterior parietal cortex, especially, the intraparietal sulcus (IPS). In a phenomenon known as number-space synaesthesia, individuals visualise numbers in specific spatial locations. The experience of a MNL for number-space synaesthetes is explicit, idiosyncratic, and highly stable over time. It remains an open question whether the mechanisms underlying numerical-spatial association are shared by synaesthetes and nonsynaesthetes. We address the neural correlates of number-space association by examining the brain response in a number-space synaestheste (MkM) whose MNL differs dramatically in its ordinality and direction from that of a control group. MkM and 15 nonsynaesthetes compared the physical size of two numbers, while ignoring their numerical value, during an event-related functional magnetic resonance imaging session (fMRI). Two factors were analysed: the numerical distance effect (NDE; e.g., 2-4 small distance vs. 1-6 large distance), and the size congruity effect (e.g., 2-8 congruent vs. 2-8 incongruent). Only for MkM, the NDE elicited significant activity in the left and right IPS, supramarginal gyrus (bilateral), and in the left angular gyrus. These results strongly support the role of the parietal cortex in the automatic coding of space and quantity in number-space synaesthesia, even when numerical values are task-irrelevant.

Social priming of hemispatial neglect affects spatial coding: Evidence from the Simon task.

In the Simon effect (SE), choice reactions are fast if the location of the stimulus and the response correspond when stimulus location is task-irrelevant; therefore, the SE reflects the automatic processing of space. Priming of social concepts was found to affect automatic processing in the Stroop effect. We investigated whether spatial coding measured by the SE can be affected by the observer's mental state. We used two social priming manipulations of impairments: one involving spatial processing - hemispatial neglect (HN) and another involving color perception - achromatopsia (ACHM). In two experiments the SE was reduced in the "neglected" visual field (VF) under the HN, but not under the ACHM manipulation. Our results show that spatial coding is sensitive to spatial representations that are not derived from task-relevant parameters, but from the observer's cognitive state. These findings dispute stimulus-response interference models grounded on the idea of the automaticity of spatial processing.

Spatial Coding as a Function of Handedness and Responding Hand: Theoretical and Methodological Implications.

The Simon effect shows that choice reactions are faster if the location of the stimulus and the response correspond, even when stimulus location is task-irrelevant. The Simon effect raises the question of what factors influence spatial coding. Until now, the effects of handedness, responding hand, and visual field were addressed in separate studies that used bimanual and unimanual tasks, providing inconclusive results. Here we aimed to close this empirical gap by looking at the effects of these variables in the same study. We used a unimanual version of a Simon task with four groups of participants: left-handed and right-handed, responding with the dominant or nondominant hand. Our results show that the Simon effect is substantially reduced in the field of the responding hand for all groups of participants, except for left-handed individuals responding with the left-hand. These findings highlight the importance of attention mechanisms in stimulus-response coding. They reflect that stimulus-response interference is influenced by hierarchical activation of response units. At a practical level, these findings call for a number of methodological considerations (e.g., handedness, responding hand, and visual field) when using stimulus-response conflict to address spatial coding and cognitive control functions in neurological populations.

What spatial coordinate defines color-space synesthesia?

Synesthesia is characterized by the association between different stimuli modalities. For example, in sequence-space synesthesia, numbers, weekdays, months, and musical tones are visualized in specific spatial locations. Although sequence-space synesthesia tends to co-occur with other types of synesthesia (e.g., grapheme-color), our knowledge about how these individuals represent space is still limited. A central issue for understanding spatial processing refers to the coordinate system used to represent spatial locations. We report on a space-color synesthete (N.W.) who vividly experiences colors in specific spatial locations. We used a task where N.W. and control subjects were required to report the location of a gray square relative to a colored square. The color of the square was task-irrelevant. Participants responded to the following trial types: (1) central trials, where one stimulus appeared on the left and the other on the right side of fixation, and (2) relative location trials, where both stimuli appeared either on the left or on the right side of fixation. Results showed that the color of the target had a strong impact on N.W.'s responses on both trial types, but not on the controls' responses. These results show that the spatial representation underlying N.W.'s synesthetic experience is automatic and sensitive to the relative location of objects.

Choosing the larger versus choosing the smaller: Asymmetries in the size congruity effect.

The size congruity effect (SiCE) shows that number and physical size interact as magnitudes. That is, response times are faster when number and size are congruent (e.g., 2 4) than when they are incongruent (e.g., 2 4). A shared representational system has been the most influential account for the SiCE. Recently, this account has been challenged by findings showing that the SiCE may be influenced by attention. The attentional contribution to the SiCE suggests that the effect is produced by an attention capture effect to the larger stimulus. Even though plausible, the attentional account overlooks 2 important factors in the study of magnitudes, namely, task (numerical vs. physical) and polarity of instructions (choose the larger vs. the smaller). We studied the influence of these factors using a size congruity task. Experiment 1 showed that the SiCE was modulated by task and instructions. In Experiment 2, we used a new set of numbers to examine a possible influence of the so-called end effect (i.e., responses to the smallest and to the largest numbers may not require number comparison). Experiment 2 successfully replicated the pattern of Experiment 1. We suggest that both feature saliency and long-term semantic processes modulate the SiCE.

Dissociating emotion and attention functions in the pulvinar nucleus of the thalamus.

OBJECTIVES: Recent models on emotional processing consider a major role for the pulvinar in the coordination of emotion processing; however, these models do not specify the type of cognitive mechanisms that the pulvinar may be subserving during emotional processing. In this opinion paper, we focus on the role of the different pulvinar subdivisions in emotion and attention. First, we review a number of neuropsychology studies and recent models that indicate that the medial nucleus of the pulvinar is critical for intact emotional processing. Then, we suggest that the role of the medial pulvinar in emotional processing is binding emotionally relevant features during working memory updating. METHOD: We carefully examined reports that describe different cognitive impairments following lesions to different pulvinar subdivisions. RESULTS: By linking these detailed neuropsychology reports to recent neuroimaging findings, we show that lesions to specific parts of the pulvinar can dramatically affect attentional processes while leaving emotion processing spared. CONCLUSIONS: We suggest a comprehensive model that specifies the functional role of the different pulvinar subdivisions in emotion-attention interplay. We propose that the impairments in emotional processing following lesions to the medial pulvinar may be related to the role of this nucleus in emotionally relevant working memory updating. The aim of this model is to foster future research examining specific functions along the different anatomical pulvinar subdivisions.

Time counts: bidirectional interaction between time and numbers in human adults.

Number is known for influencing time processing, but to what extent time influences number in human adults is unclear. We investigated possible bidirectional interactions (number on time and time on number) using a novel Stroop-like task; participants compared numbers or temporal durations in congruent (larger number presented for longer duration) or incongruent conditions (smaller number presented for longer duration). Time and number tasks were presented in different blocks (Experiment 1) or within the same block of trials with task instructions provided at the offset of the stimuli (Experiment 2). Analyses of response times (RTs) and their distribution revealed that number affected time from early RTs, and time affected number at late RTs - an asymmetry observed only when time and number tasks were presented in separate blocks. Thus, carefully chosen tasks and appropriate data analysis can reveal bidirectionality between time and number, consistent with shared magnitude or decision mechanisms.

Numerical-spatial representation affects spatial coding: binding errors across the numerical distance effect.

Does numerical-spatial representation affect feature binding? Studies of visual attention show that poor spatial coding leads to illusory conjunctions (ICs). In numerical cognition, it has been shown that numbers and space are not totally dissociated. This association underlies the numerical distance effect (DE): faster responses as the distance between the compared digits becomes larger (2 7 vs. 2 4). We used the DE to test whether numerical-spatial representation is available to visual processes that rely on spatial coding, such as feature binding. Participants reported the larger of two colored numbers. Both numerical distance (distances 2 and 5) and number-space congruity (e.g., congruent pair, 1 3; incongruent pair, 3 1) were analyzed. Results showed a higher proportion of ICs for distance 2 than for distance 5, providing strong evidence that numerical-spatial representation (1) entails a strong location code and (2) is available to visual processes that rely on location information.

Perceiving numbers influences actions in number-space synesthesia.

Number and space are spontaneously linked in human cognition and have been metaphorically described as a 'mental number line'. In number-space synesthetes (NSS), numbers are visualized in specific spatial arrays, in an idiosyncratic and explicit manner. Here we tested whether the numerical-spatial association that characterizes NSS has the potential to affect individual's actions when the number is not a task-relevant feature. We used a Simon task that implies stimulus-response matching. Task-irrelevant Arabic numerals (1, 4, 6, 9) appeared simultaneously at the same location as a colored target. A group of 15 age-matched controls and 4 NSS completed a 2×2 within-subjects design consisting of Simon (compatible and incompatible) and number-space (congruent and incongruent) trials. Mean reaction time (RT) and RT cumulative distribution functions across Simon and number-space conditions for both NSS and controls were analyzed. Relative to controls, synesthetes' RTs were overall affected by the number-space mapping. Moreover, synesthetes' Simon effects occurred at later response times. These results provide strong evidence that numbers are cognitively represented as action codes and that the strength of the association shapes the impact of the numerical representation on individuals' actions.