Affective evaluation of food images according to stimulus and subject characteristics.

BACKGROUND: The food-rich environment in which we live makes the regulation of food choices a very complex phenomenon determined by many factors, as well as their interactions. Much evidence suggests that the sensory perception of food can be considered as a central factor affecting individual food choices. Despite this, the approaches used to study the various food aspects usually do not distinguish between different types of food. METHODS: In the present study, a large and heterogeneous sample of 1149 participants aged 7-90 years was asked to judge food images that were labelled differently (i.e. Raw versus Cooked, Natural versus Transformed and Simple versus Complex) with respect to arousal, valence, typicality and familiarity. RESULTS: We observed that, across food dimensions (i.e., Raw versus Cooked, Natural versus Transformed and Simple versus Complex), arousal, valence and typicality judgments were principally affected by a subjective hunger level and gender (and their interaction) and, to a lesser extent, by age. CONCLUSIONS: As a whole, our findings suggest that the level of transformation (which includes cooking) and the complexity of a foodstuff could at least partially affect food processing, entailing that future research should also address these features.

Neuromagnetic responses reveal the cortical timing of audiovisual synchrony.

Multisensory processing involving visual and auditory inputs is modulated by their relative temporal offsets. In order to assess whether multisensory integration alters the activation timing of primary visual and auditory cortices as a function of the temporal offsets between auditory and visual stimuli, a task was designed in which subjects had to judge the perceptual simultaneity of the onset of visual stimuli and brief acoustic tones. These were presented repeatedly with three different inter-stimulus intervals that were chosen to meet three perceptual conditions: (1) physical synchrony perceived as synchrony by subjects (SYNC); (2) physical asynchrony perceived as asynchrony (ASYNC); (3) physical asynchrony perceived ambiguously (AMB, i.e. 50% perceived as synchrony, 50% as asynchrony). Magnetoencephalographic activity was recorded during crossmodal sessions and unimodal control sessions. The activation of primary visual and auditory cortices peaked at a longer latency for the crossmodal conditions as compared to the unimodal conditions. Moreover, the latency in the auditory cortex was longer in the SYNC than in the ASYNC condition, whereas in the visual cortex the latency in the AMB condition was longer than in the ASYNC condition. These findings suggest that multisensory processing affects temporal dynamics already in primary cortices, that such activity can differ regionally and can be sensitive to the temporal offsets of multisensory inputs. In addition, in the AMB condition the conscious awareness of asynchrony might be associated to a later activation of the primary auditory cortex.

Inhibitory effect of voluntary movement preparation on cutaneous heat pain and laser-evoked potentials.

In our study, preparation of voluntary movement was used to physiologically activate the motor cortex areas and the effect of this activation on CO(2) laser-evoked potentials (LEPs) was explored. LEPs were recorded from 31 scalp electrodes in 10 healthy subjects after painful stimulation of the right C6-C7 skin dermatomes. LEP stimuli were delivered in the time interval between a visual warning stimulus followed after 1 s. by an imperative stimulus. The imperative stimulus triggered: (i) no task in the baseline condition (Pain); (ii) flexion-extension movements of the second finger of the right hand in the movement condition (Pain + Movement); (iii) cognitive task (mathematic computation) in the distraction condition (Pain + Cognition). The experimental conditions were also repeated during application of laser stimuli on the left C6-C7 skin dermatomes. Compared with the baseline condition (no task required), during preparation of right-hand voluntary movement there was a significant reduction in LEP amplitude and subjective pain rating after right- but not after left-hand stimulation, which suggests that the observed effect cannot be attributed to a nonspecific reduction in attention toward painful stimulus. During preparation of a cognitive task, LEP amplitude was reduced compared to baseline. Our results represent the first neurophysiological suggestion that physiological activation of the motor cortex, occurring during movement preparation, inhibits cortical pain processing by a centrifugal mechanism.

Decrease of functional coupling between left and right auditory cortices during dichotic listening: an electroencephalography study.

The present study focused on functional coupling between human bilateral auditory cortices and on possible influence of right over left auditory cortex during dichotic listening of complex non-verbal tones having near (competing) compared with distant non-competing fundamental frequencies. It was hypothesized that dichotic stimulation with competing tones would induce a decline of functional coupling between the two auditory cortices, as revealed by a decrease of electroencephalography coherence and an increase of directed transfer function from right (specialized for the present stimulus material) to left auditory cortex. Electroencephalograph was recorded from T3 and T4 scalp sites, overlying respectively left and right auditory cortices, and from Cz scalp site (vertex) for control purposes. Event-related coherence between T3 and T4 scalp sites was significantly lower for all electroencephalography bands of interest during dichotic listening of competing than non-competing tone pairs. This was a specific effect, since event-related coherence did not differ in a monotic control condition. Furthermore, event-related coherence between T3 and Cz and between T4 and Cz scalp sites showed no significant effects. Conversely, the directed transfer function results showed negligible influence at group level of right over left auditory cortex during dichotic listening. These results suggest a decrease of functional coupling between bilateral auditory cortices during competing dichotic stimuli as a possible neural substrate for the lateralization of auditory stimuli during dichotic listening.

Gamma-Hydroxybutyrate inhibits excitatory postsynaptic potentials in rat hippocampal slices.

Gamma-Hydroxybutyrate (GHB) has been shown to mimic different central actions of ethanol, to suppress alcohol withdrawal syndrome, and to reduce alcohol consumption both in rats and in humans. The aim of the present study was to determine if GHB shared with alcohol the ability to inhibit glutamate action at both NMDA and AMPA/kainate receptors. The NMDA or the AMPA/kainate receptors-mediated postsynaptic potentials were evoked in CA1 pyramidal neurons by stimulation of Schaffer-collateral commissural fibers in the presence of CGP 35348, bicuculline to block the GABA(B) and GABA(A) receptors, and 10 microM 6,7-dinitroquinoxaline-2,3-dione (DNQX) or 30 microM DL-2-amino-5-phosphonovalerate (d-APV) to block AMPA/kainate or NMDA receptors, respectively. GHB (600 microM) produced a depression of both NMDA and AMPA/kainate receptors-mediated excitatory postsynaptic potentials with recovery on washout. The GHB receptors antagonist, NCS-382, at the concentration of 500 microM had no effect per se on these responses but prevented the depressant effect of GHB (600 microM) on the NMDA and AMPA/kainate-mediated responses. In the paired-pulse experiments, GHB (600 microM) depressed the amplitude of the first and the second evoked AMPA/kainate excitatory postsynaptic potentials, and significantly increased the paired-pulse facilitation (PPF). These results suggest that GHB inhibits excitatory synaptic transmission at Schaffer-collateral commissural-pyramidal neurons synapses by decreasing the probability of release of glutamate.

Laterality in the perception of temporal cues of musical timbre.

Laterality in the perception of non-stationary aspects of musical timbre was investigated in 54 right-handed non-musicians. Timbre differences were produced by altering the amplitude envelope of a steady-state complex tone. Two single-choice tests with attention directed to one ear were used--a dichotic test and a monaural test with contralateral white noise. Dependent variables were reaction time and accuracy. Both tests showed a significant left ear advantage for reaction time. For the accuracy variable, a significant left ear advantage was found only in the monaural test. Results are briefly discussed in terms of their compatibility with the generally accepted notion that spectral and temporal integrations of sounds are primarily functions of the right and left hemisphere, respectively.