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Reasoning is the ability to formulate inferences or conclusions from available information. The two major types, deductive and inductive, are thought to rely on distinct cognitive mechanisms and recruit separate brain areas. Neuroimaging studies yield mixed results; some found the left inferior frontal gyrus (IFG) activations for deductive reasoning and the left dorsolateral prefrontal cortex (DLPFC) for inductive reasoning. This assumption was put to the test in the present study. In two double-blinded, sham-controlled experiments, high-definition transcranial direct current stimulation (HD-tDCS) was used to systematically explore the left IFG's and DLPFC's causal role in deductive and inductive reasoning. Participants with no formal training in logic judged deductive and inductive arguments before and after 10 minutes of anodal, cathodal, or sham tDCS of the left IFG (Experiment 1, n = 20) or left DLPFC (Experiment 2, n = 21). Left IFG anodal tDCS impairs reaction times (RTs) for easy categorical (p = <.001) and propositional (p =.025) deductive arguments and the accuracy for easy inductive propositional arguments (p =.003). Meanwhile, regardless of the active stimulation conditions, left DLPFC tDCS shortens RTs (anodal: p = <.001, cathodal: p =.014) and increases accuracy (anodal: p =.029, cathodal: p =.001) for difficult categorical inductive arguments, but decreases accuracy (anodal: p =.027, cathodal: p = <.001) for difficult propositional inductive arguments. The overall results showed a partial dissociation of the left frontal lobe areas subserving the two types of reasoning and argument difficulty-dependent stimulation effects. This study extends knowledge of the neural basis of reasoning and hopefully inspires interventions that could augment reasoning impairments associated with normal aging and brain lesions. [ABSTRACT FROM AUTHOR]

The current study on German investigates Event-Related brain Potentials (ERPs) for the perception of sentences with intonations which are infrequent (i.e. vocatives) or inadequate in daily conversation. These ERPs are compared to the processing correlates for sentences in which the syntax-to-prosody relations are congruent and used frequently during communication. Results show that perceiving an adequate but infrequent prosodic structure does not result in the same brain responses as encountering an inadequate prosodic pattern. While an early negative-going ERP followed by an N400 were observed for both the infrequent and the inadequate syntax-to-prosody association, only the inadequate intonation also elicits a P600.

In this functional MRI experiment, encoding of objects was associated with activation in left ventrolateral prefrontal/insular and right dorsolateral prefrontal and fusiform regions as well as in the left putamen. By contrast, correct recognition of previously learned objects (R judgments) produced activation in left superior frontal, bilateral inferior frontal, and right cerebellar regions, whereas correct rejection of distractor objects (N judgments) was associated with activation in bilateral prefrontal and anterior cingulate cortices, in right parietal and cerebellar regions, in the left putamen, and in the right caudate nucleus. The R minus N comparison showed activation in the left lateral prefrontal cortex and in bilateral cingulate cortices and precunei, while the N minus R comparison did not reveal any positive signal change. These results support the view that similar regions of the frontal lobe are involved in episodic encoding and retrieval processes, and that the successful episodic retrieval of newly learned objects is mainly based on a frontoparietal network.

Functional MRI was used to investigate brain activation in healthy volunteers during encoding of unfamiliar faces as well as during correct recognition of newly learned faces (CR) compared to correct identification of distractor faces (CF), missed alarms (not recognizing previously presented faces, MA), and false alarms (incorrectly recognizing newly presented faces, FA). Encoding was associated with frontal, occipital/fusiform, thalamic, and cerebellar activation. CR produced activation in frontal and cerebellar regions, whereas CF activated frontal and occipitotemporal regions as well as the thalamus. In contrast, MA was associated with frontal and thalamic activation, and FA with frontal activation. The CR minus CF comparison showed left lateral prefrontal and parietal activation, while no suprathreshold positive signal changes were detected when subtracting the other conditions (CR minus MA, CR minus FA, and vice versa). These results support the view that the successful episodic retrieval of newly learned faces is based on a dorsal visual stream mechanism.

Humans show systematic congruency effects due to irrelevant variations of the numerical value or the physical size of digits in judgments about either of these 2 attributes alone. According to influential models (e.g., J. Tzelgov, J. Meyer, & A. Henik, 1992), these effects are characterized by genuine asymmetries of size and number processing not accounted for by simple relative speed considerations, whereas some recent work (e.g., A. Pansky & D. Algom, 1999) partly challenges this view. This article presents 2 qualitative gradient-based predictions made by relative speed models and a diffusion-based implementation of the relative speed view to quantitatively account for response times and error rates in comparative judgments of digits. The results of 2 experiments using a completely task-symmetric design are in accord with these detailed predictions; they are also consistent with the view that both number and size are converted into magnitude representations of similar structure.