Cardinal and ordinal processing in spatial neglect

Poster (2016, January)

Patients with spatial neglect do not only have difficulties in orienting attention in physical space but also in representational space, especially with respect to the mental representation of numbers ... [more ▼]

Patients with spatial neglect do not only have difficulties in orienting attention in physical space but also in representational space, especially with respect to the mental representation of numbers. Indeed, in a study by Zorzi et al. (2012) neglect patients were particularly slow when asked to compare the number 4 to the standard number 5, suggesting difficulties to process numbers on the left side of an internal standard. This difficulty was observed in a magnitude judgement, but not in a parity task, implying a dissociation between explicit and implicit processing of numerical magnitude. The present study aimed at replicating these findings and extending them to non-numerical sequences in order to complement the data obtained on bisection tasks (Zamarian, et al., 2007). Sixteen right-sided brain damaged patients with neglect (N+ =6; 4 females; all right handers; mean age: 55 +/- 8,7) and without neglect (N- =10; 2 females; all right hander; mean age: 48 +/- 6.2) participated in the study. They were administered the following tasks: a magnitude and a parity judgement task; an ordinal judgement task on numbers and on letters and a consonant/vowel classification task. For each task and each patient, a linear regression was computed in which the difference between the response times for the left effector (index finger) and the right effector (middle finger) was predicted by number magnitude. A negative slope will indicate the presence of a SNARC-like effect. We compared the negative slopes of the two patient groups using a Chi-square. Considering the proportion of SNARC-like effects, it appeared that, on one hand, N+ patients showed fewer SNARC-like effects than N- patients during magnitude judgements on numbers. Thus confirming the findings by Zorzi et al. (2012). On the other hand, N+ patients behaved similarly to N- patients for the parity judgements on numbers and for the order judgements both on numbers and letters. This last result suggest a dissociation between the spatial representation of magnitude and of order in N+ patients. These results point towards a specific impairment in explicit access to number magnitude in spatial hemineglect. [less ▲]

Does body motion influence arithmetic

Poster (2015, March)

« Embodiment theory » proposes that bodily actions impact the quality of mental representations. Two recent studies (Loetscher, et al., 2008; Hartmann, et al., 2011) have shown that leftward movements of ... [more ▼]

« Embodiment theory » proposes that bodily actions impact the quality of mental representations. Two recent studies (Loetscher, et al., 2008; Hartmann, et al., 2011) have shown that leftward movements of the head or the body enhanced small number generation while rightward movements increased the generation of larger numbers. The present study aimed to investigate the influence of passive whole-body movement on arithmetic-problem solving. Our design was elaborated in the context of operational momentum effect (Pinhas, & Fischer, 2008; McCrink, et al., 2007). In the domain of arithmetic this effect refers to the fact that outcomes of additions are systematically estimated to be larger than the outcomes of subtractions and vice versa for subtraction (Knops, et al., 2009; Lindemann, et al., 2011). Interestingly this bias is present for non-carry but not for carry problems. To account for the operational momentum effect it has been proposed that subtractions involve an attentional motion towards the left of the mental number line and additions towards the right inducing the above-mentioned under- and over-estimation. In line with these findings we reasoned that passive body motion might orient attention towards the side of the body movement and consequently enhance the attentional shifts supposed to underlie the operational momentum effects that occur during numerical tasks. In the present paradigm participants were sitting blindfolded on a swivel chair. While they were rotated alternatively 180° towards the left and the right with a pace of 49°/sec., they were asked to orally solve different kinds of calculations presented via headphones. Calculations consisted in additions and subtractions (first operand: from 1 to 98; second operand: from 1 to 13 and results: from 3 to 89) that were composed of carry and non-carry problems and had different levels of difficulty (easy: results from 1 to 9; medium: results from 11 to 19; difficult: from 21 to 89). Contrary to our predictions, results indicate that the direction of passive body motion (i.e. leftwards vs. rightwards) did not influence arithmetic performance. Indeed the ANOVA for repeated measures with the factor Motion (left, right), Problem type (carry, non-carry) and Operation type (addition, subtraction) revealed no main effect of motion (F(1,33)= 0,856, p=0.361). In contrast we observed a main effect of Problem type (F(1,33)=29.065, p<0.001), a main effect of Operation type (F(1,33)= 20,721, p<0.001) and a significant interaction of Problem type x Operation type (F(1,30)=5.605,p=0.024). As would be expected from the results observed with classical stationary experiment settings, participants were more accurate while solving additions than subtractions and made less errors with non-carry problems. Moreover the carry effect was larger for subtractions than additions. Analyses of the reaction times led to the same conclusions. These results indicate that orally solving arithmetic problems is not influenced by the direction (leftwards vs. rightwards) of passive rotary body-motion. This finding contrasts with previous observations that active head movements and/or passive translational movements impacts numerical task performance. Future studies which systematically contrast the effects of the different movement types on numerical tasks should help to clarify this discrepancy. [less ▲]