Emotion and attention interaction studied through event-related potentials.

Several studies on hemodynamic brain activity indicate that emotional visual stimuli elicit greater activation than neutral stimuli in attention-related areas such as the anterior cingulate cortex (ACC) and the visual association cortex (VAC). In order to explore the temporo-spatial characteristics of the interaction between attention and emotion, two processes characterized by involving short and rapid phases, event-related potentials (ERPs) were measured in 29 subjects using a 60-electrode array and the LORETA source localization software. A cue/target paradigm was employed in order to investigate both expectancy-related and input processing-related attention. Four categories of stimuli were presented to subjects: positive arousing, negative arousing, relaxing, and neutral. Three attention-related components were finally analyzed: N280pre (from pretarget ERPs), P200post and P340post (both from posttarget ERPs). N280pre had a prefrontal focus (ACC and/or medial prefrontal cortex) and presented significantly lower amplitudes in response to cues announcing negative targets. This result suggests a greater capacity of nonaversive stimuli to generate expectancy-related attention. P200post and P340post were both elicited in the VAC, and showed their highest amplitudes in response to negative- and to positive-arousing stimuli, respectively. The origin of P200post appears to be located dorsally with respect to the clear ventral-stream origin of P340post. The conjunction of temporal and spatial characteristics of P200post and P340post leads to the deduction that input processing-related attention associated with emotional visual stimulation involves an initial, rapid, and brief "early" attentional response oriented to rapid motor action, being more prominent towards negative stimulation. This is followed by a slower but longer "late" attentional response oriented to deeper processing, elicited to a greater extent by appetitive stimulation.     

Expected taste intensity affects response to sweet drinks in primary taste cortex

Expectations about a food can impact on its taste, but this may represent a perceptual change or a bias in response at the decision-making stage. We hypothesised that expectation of taste intensity should be underpinned by modulation of activity in primary taste cortex. Using functional magnetic resonance imaging, we found that expecting a very sweet drink, but receiving a less sweet drink, enhanced the reported sweetness and bolstered activity in taste cortex, relative to a less sweet drink without this expectation. The activation overlapped with primary taste cortex activation found in 11 recent taste studies. Our findings provide evidence that taste expectation modulates activity in an area consistently reported as primary taste cortex, implying that expectation effects do indeed impact on taste perception.     

Inverted event-related potentials response to illusory contour in boys with autism

We examined the hypothesis of lower-level processing abnormalities related to perceptual grouping in boys with autism aged 3-6 years. We investigated event-related potentials response to visual elements that either formed perceptually coherent illusory contour or were arranged in a noncoherent way. The results showed that in healthy boys the illusory contour as compared with control stimulus elicited enhanced negativity of N1 peak (C effect), which has been previously found in adults. Autistic boys demonstrated the reliable inverted illusory contour effect, that is, more positive N1 amplitude to illusory contour. We hypothesized that boys with autism were sensitive to difference between illusory contour and control figures basing on collinearity processing mechanisms implemented in neural circuitry of primary visual cortex.     

Canine taste nerve responses to monosodium glutamate and disodium guanylate: differentiation between umami and salt components with amiloride.

It has been argued whether the 'umami substances' such as monosodium glutamate (MSG) and disodium 5'-guanylate (GMP) stimulate the salt receptor or the unique receptor to the umami substances. We examined effects of amiloride, which inhibited the canine chorda tympani nerve responses to salts such as NaCl, KCl and NH4Cl, in a competitive manner, on the nerve responses to the umami substances and differentiated between the umami and salt components. Amiloride shifted the dose-response curves for MSG to a higher concentration region, suggesting that amiloride inhibits the response to MSG in a competitive manner. The response to GMP alone and that induced by synergism between relatively low concentrations of MSG and GMP were not inhibited by amiloride. These results suggested that the response to MSG alone is the salt response and the response to GMP alone or that induced by the synergism is the umami response. The presence of MSG shifted the dose-response curves for GMP to a lower concentration region, suggesting that MSG increases the affinity of GMP to umami receptors. The present results favor the conclusion that GMP acts as an agonist and MSG acts as a modulator for the umami receptor in the dog. The synergism can be explained by an allosteric model where the umami receptor is assumed to have two binding sites, one for GMP and another for MSG.     

Selective attention to sound location or pitch studied with event-related brain potentials and magnetic fields

Event-related brain potentials (ERPs) and magnetic fields (ERFs) were used to compare brain activity associated with selective attention to sound location or pitch in humans. Sixteen healthy adults participated in the ERP experiment, and 11 adults in the ERF experiment. In different conditions, the participants focused their attention on a designated sound location or pitch, or pictures presented on a screen, in order to detect target sounds or pictures among the attended stimuli. In the Attend Location condition, the location of sounds varied randomly (left or right), while their pitch (high or low) was kept constant. In the Attend Pitch condition, sounds of varying pitch (high or low) were presented at a constant location (left or right). Consistent with previous ERP results, selective attention to either sound feature produced a negative difference (Nd) between ERPs to attended and unattended sounds. In addition, ERPs showed a more posterior scalp distribution for the location-related Nd than for the pitch-related Nd, suggesting partially different generators for these Nds. The ERF source analyses found no source distribution differences between the pitch-related Ndm (the magnetic counterpart of the Nd) and location-related Ndm in the superior temporal cortex (STC), where the main sources of the Ndm effects are thought to be located. Thus, the ERP scalp distribution differences between the location-related and pitch-related Nd effects may have been caused by activity of areas outside the STC, perhaps in the inferior parietal regions.     

Component enhancement through temporal compression and expansion of event-related potentials

A technique is described in which wave forms are temporally compressed or expanded to provide optimal correlation with a superaveraged template. In certain instances, this filter can be applied more appropriately than other filters which shift or rotate wave forms. A 2-part experiment was carried out in which the efficacy of the filter was evaluated for responses of (a) moderate size and consistent latency, and (b) small amplitude and variable latency. The filter was effective in enhancing data for the small, variable responses while it had no significant effect on more consistent data. Possible functional interpretations of latency adjustment techniques are presented.     

Chemospecific deficits in taste sensitivity following bilateral or right hemispheric gustatory cortex lesions in rats

Our prior studies showed bilateral gustatory cortex (GC) lesions significantly impair taste sensitivity to salts (NaCl and KCl) and quinine (“bitter”) but not to sucrose (“sweet”). The range of qualitative tastants tested here has been extended in a theoretically relevant way to include the maltodextrin, Maltrin, a preferred stimulus by rats thought to represent a unique taste quality, and the “sour” stimulus citric acid; NaCl was also included as a positive control. Male rats (Sprague–Dawley) with histologically confirmed neurotoxin-induced bilateral (BGCX, n = 13), or right (RGCX, n = 13) or left (LGCX, n = 9) unilateral GC lesions and sham-operated controls (SHAM, n = 16) were trained to discriminate a tastant from water in an operant two-response detection task. A mapping system was used to determine placement, size, and symmetry (when bilateral) of the lesion. BGCX significantly impaired taste sensitivity to NaCl, as expected, but not to Maltrin or citric acid, emulating our prior results with sucrose. However, in the case of citric acid, there was some disruption in performance at higher concentrations. Interestingly, RGCX, but not LGCX, also significantly impaired taste sensitivity, but only to NaCl, suggesting some degree of lateralized function. Taken together with our prior findings, extensive bilateral lesions in GC do not disrupt basic taste signal detection to all taste stimuli uniformly. Moreover, GC lesions do not preclude the ability of rats to learn and perform the task, clearly demonstrating that, in its absence, other brain regions are able to maintain sensory-discriminative taste processing, albeit with attenuated sensitivity for select stimuli.     

Strategic retrieval and retrieval orientation in reality monitoring studied by event-related potentials (ERPs)

Reality monitoring requires the differentiation between perceived and imagined events or between our own actions and the actions of others. The role of control processes in reality monitoring is yet not fully understood. In the current event-related potential (ERP) study, we investigated such control processes in the form of retrieval orientation and strategic retrieval of nontarget information. At study, complete or incomplete object words were presented in sentences. Participants had to identify the words as the subject of the sentence (perceive condition) or had to complete them upon presentation of a word fragment (self-generate condition). The participants' memory accuracy was better for generated items than for perceived items, as tested in a subsequent memory exclusion task. Comparison of ERPs to new items between the two test conditions (i.e. assessing retrieval orientation) showed more positive ERPs when generated object names were targeted. Retrieval orientation also modulated the early midfrontal old/new effect: Items of the self-generate condition elicited this effect irrespective of their target/nontarget status, while in response to the less well remembered items of the perceive condition it was only found when these items were defined as targets. Target retrieval (as reflected in the left-parietal old/new effect) occurred in both test conditions, but nontarget retrieval was observed only for generated items (when perceived items were targeted). Current findings indicate that retrieval orientation can modulate familiarity-related processes. The selective occurrence of nontarget retrieval for generated items corroborates the concept that the ease with which nontarget information can be accessed promotes nontarget retrieval.     

Recording of event-related potentials (P300) from human cortex.

Auditory event-related potentials were recorded simultaneously from chronically implanted subdural electrodes and from scalp electrodes in three patients who were being evaluated for surgical treatment of epilepsy. These three cases showed clearly defined scalp-P300 and scalp-N300. A cortex-P300 was recorded from the midtemporal area, and a cortex-N300 was recorded from the inferior frontal area with some reflection at the basal temporal region. There were no potentials from an interhemispheric region. We could not observe any component from the cortex studied corresponding to scalp-recorded N200. Therefore, while the activity generated from the mesial temporal lobe may only make minor contributions to scalp-P300, that generated from the midtemporal area might make a major contribution to the scalp-P300. Additionally, generators of N200, P300, and N300 are different from each other. These findings, together with previous reports regarding the generator source of P300, also suggest that P300 is a complex arising from multifactorial generator sources, including the midtemporal and inferior frontal area.     

The evaluation of brain activity in response to taste stimuli--a pilot study and method for central taste activation as assessed by event-related fMRI

BACKGROUND: Brain pathways contribute to the regulation of appetite behaviors, and advancements in brain imaging offer new opportunities in determining whether disturbances of these pathways play a role in pathological feeding behaviors in humans. We developed a standardized method for the assessment of brain activation in response to taste stimuli. METHODS: Five healthy control women were positioned in a 1.5 T GE magnet resonance (MR) scanner for functional MR imaging (fMRI). They received 1.0 cm3 samples of 1 M glucose solution or artificial saliva (25 mM KCl, 2 mM NaHCO3). Fluid challenges were delivered by a programmable syringe pump (J-Kem Scientific, St. Louis, MO). E-Prime software (Psychology Software Tools Inc., Pittsburgh, PA) coordinated taste stimulation with MR scanning. Data were analyzed using NeuroImaging software (NIS). RESULTS: Healthy women showed increased orbitofrontal cortex activation when glucose was compared to artificial saliva. In addition, mesial and lateral temporal cortical regions contrasted glucose from artificial saliva. CONCLUSIONS: This study demonstrates a design for the systematic study of brain activation after taste stimulation using fMRI and computer controlled stimulus delivery. The results are consistent with previous studies, showing activation in higher order brain centers that are involved in emotional coding of taste experience.     

On-line psychophysical data acquisition and event-related fMRI protocol optimized for the investigation of brain activation in response to gustatory stimuli

An experimental method for event-related functional magnetic resonance imaging that allows for the presentation of several chemosensory stimuli in the oral cavity during the same run, the collection of psychophysical measures (intensity or pleasantness) during the presentation of the stimuli, and the analysis of the data in an event-related fashion are described. The automatic pumps used to present taste stimuli allowed for multiple tastes to be delivered in small amounts under computer control. Psychophysical ratings of pleasantness or intensity were collected after each presentation of a taste stimulus and water, with the general labeled magnitude scale, using a joystick that controlled the movement of an arrow on the visual display. Performing these cognitive tasks required that the participant remained focused, and aided in the interpretation of the data collected. The perceived pleasantness differed across stimuli for all conditions; however, pleasantness ratings for the same stimulus displayed consistency, over the duration of the run and before each scan on separate days. Activation in response to sucrose and caffeine while the participant rated pleasantness was found in the insula, frontal operculum, rolandic operculum and orbitofrontal cortex which is consistent with previous taste fMRI studies.     

Characterization of umami receptor and coupling G protein in mouse taste cells

Taste receptor cells (TRCs) express multiple umami receptors. We performed physiological investigations to determine whether umami-responding cells in taste buds possess G protein-coupled receptors and to determine what type of G proteins exist if any. To clarify the components that participate in intracellular umami signal transduction in mouse, we recorded the activation of TRCs. TRCs treated with the G protein inhibitor GDP-beta-S lost umami-induced inward currents. Treatment with the Galphai inhibitor, pertussis toxin, did not increase the intracellular Ca2+ level in many TRCs. Immunohistochemical analysis revealed that a subset of TRCs responding to umami stimuli expressed alpha-gustducin. Thus, we demonstrated that umami stimuli were received by G protein-coupled receptors that function together with some of the Galphai family members.     

Electrophysiological and behavioural characterization of gustatory responses to antennal 'bitter' taste in honeybees

We combined behavioural and electrophysiological experiments to study whether bitter taste is perceived at the antennal level in honeybees, Apis mellifera. Our behavioural studies showed that neither quinine nor salicin delivered at one antenna at different concentrations induced a retraction of the proboscis once it was extended in response to 1 M sucrose solution delivered to the opposite antenna. Bees that extended massively their proboscis to 1 M sucrose responded only partially when stimulated with a mixture of 1 M sucrose and 100 mM quinine. The mixture of 1 m sucrose and 100 mM salicin had no such suppressive effect. No behavioural suppression was found for mixtures of salt solution and either bitter substance. Electrophysiological recordings of taste sensillae at the antennal tip revealed sensillae that responded specifically either to sucrose or salt solutions, but none responded to the bitter substances quinine and salicin at the different concentrations tested. The electrophysiological responses of sensillae to 15 mM sucrose solution were inhibited by a mixture of 15 mM sucrose and 0.1 mM quinine, but not by a mixture of 15 mM sucrose and 0.1 mM salicin. The responses of sensillae to 50 mM NaCl were reduced by a mixture of 50 mm NaCl and 1 mM quinine but not by a mixture of 50 mM NaCl and 1 mM salicin. We concluded that no receptor cells for the bitter substances tested, exist at the level of the antennal tip of the honeybee and that antennal bitter taste is not represented as a separate perceptual quality.     

Differential involvement of gustatory insular cortex and amygdala in the acquisition and retrieval of conditioned taste aversion in rats.

Lesion studies of the role of the gustatory insular cortex (GC) and amygdala (Am) in conditioned taste aversion (CTA) are confounded by the irreversibility of the intervention. Functional ablation methods allow more specific influencing of different phases of CTA acquisition and retrieval. Bilateral tetrodotoxin (TTX) blockade of GC (10 ng) or Am (3 ng) before or after saccharin drinking in rats with chronically implanted intracerebral cannulae showed that GC is indispensable for the initial processing of the taste stimulus but not for the association of the gustatory trace with the symptoms of LiCl poisoning. Gustatory signals can by-pass the blocked Am, the inactivation of which, however, impairs the gustatory trace-poisoning association. TTX injection into both GC and Am impairs CTA retrieval more than isolated blockade of either of these structures. It is argued that GC and Am implement processing of gustatory and visceral signals, respectively, but that formation and consolidation of the CTA engram proceeds outside forebrain, probably at the level of the brainstem.     

The effects of frontal cortex lesions on event-related potentials during auditory selective attention

We compared electrophysiological indices of auditory selective attention in control subjects and in patients with unilateral lesions of the dorsolateral frontal lobes. In control subjects, ERPs following attended tones showed an enhanced negativity from 80 to 500 msec post-stimulus which had a different topographic distribution than the N120. Lesions of the frontal lobes reduced the attention-related negativity and impaired behavioral performance. The ERP reductions were equivalent in recordings obtained from electrodes placed over the damaged and intact cortex. A difference was noted between left and right frontal groups as a function of ear of delivery of the stimuli. Patients with left frontal lesions showed reduced attention effects following tones presented to either ear. Patients with right frontal lesions showed intact attention effects to right ear tones, but no attention-related negativity to left ear tones. When the left and right frontal groups were considered together, tones in ignored channels produced larger responses when presented to the ear contralateral to damaged cortex. These results underline the important role of the frontal lobes in processes of selective attention. Although the endogenous negativity produced in selective attention tasks does not appear to originate in dorsolateral frontal cortex, the frontal lobes exhibit a modulating influence upon it. In addition, the endogenous attention related negativity and exogenous N120 components apparently arise from different neural generators.     

Modifications of cognitive and motor tasks affect the occurrence of event-related potentials in the human cortex

This study concerns the question of how task modification affects the frequency occurrence of event-related potentials (ERP) inside the active cortical areas. In 13 candidates for epilepsy surgery, 156 sites in the temporal (74), frontal (73), and parietal (9) cortices were recorded by means of depth and subdural electrodes. Four modifications of the somatosensory evoked P3-like potentials were performed; (i) an oddball paradigm with silent counting of target stimuli (P3c); (ii) an oddball paradigm with a hand movement in response to target stimuli (P3m); (iii) an S1-S2 paradigm, ERP in the P300 time window after the S2 stimulus, with silent counting of target stimuli (S2c), and (iv) an S1-S2 paradigm with a hand movement in response to target stimuli (S2m). In comparing the oddball paradigms with the S1-S2 (contingent negative variation, CNV) paradigms, four regions emerge that are significantly linked with the oddball P3; the prefrontal cortex, the cingulate, the amygdalo-hippocampal complex, and the lateral temporal cortex. A prominent role of the cingulate and the fronto-orbital cortex in the cognitive processing of movement was supported when tasks with identical cognitive loads but different required responses were compared. Even relatively simple cognitive tasks activate many cortical regions. The investigated areas were activated in all tests; however, small regions in each field were active or inactive in relation to the nature of the task. The study indicates a variable and task-dependent internal organization of a highly complex and widely distributed system of active cortical areas.     

卒中后抑郁患者的交感神经皮肤反应与事件相关电位对照研究

目的探讨交感神经皮肤反应(SSR)与事件相关电位(ERP)对卒中后抑郁患者的诊断价值。方法对55例卒中后抑郁患者和52例正常健康者分别进行了SSR和ERP测定,并将结果加以比较。结果卒中后抑郁组中SSR和ERP测定中的P300成分异常率分别为87.3%(48/55)和83.6%(46/55),两者异常吻合率为76.4%(42/55)。卒中后抑郁组SSR测定结果中,SSR潜伏期和波幅值较对照组延长和降低,其差异具有显著性(P<0.01),ERP测定中N2、P3波潜伏期和P3波幅较对照组分别延长和降低,存在显著性差异(P<0.01)。其中N2、P3波潜伏期与SSR测定中潜伏期以及波幅与波幅之间呈正相关(r=0.29~0.36,P<0.01),而两者潜伏期与波幅之间呈负相关(r=-0.32~-0.33,P<0.01)。结论交感神经皮肤反应和事件相关电位测定可作为卒中后抑郁患者的诊断指标应用于临床。     

Long latency event-related potentials in rats: response of amygdala, nucleus accumbens, dorsal hippocampus and frontal cortex to changes in reward characteristics of conditioned stimuli

Circuits involving major afferents to the ventral striatum from the frontal cortex, amygdala and hippocampus have been implicated in the selective processing of conditioned stimuli predictive of ‘important events' or reward-related processes. We utilized an animal model of event-related potentials (ERPs) to explore the relationship between these brain areas during the performance of a conditioning/extinction task. Significant reductions in the N1 component in cortex and P2 component in amygdala of the rat ERP were found as a consequence of removal of the food reward previously associated with the stimuli. Lesions of the nucleus basalis magnocellularis were without effect on the pattern of ERP morphology changes associated with the removal of the reward. Since the N1 component of the ERP has been linked to attentional processes, these studies suggest that elimination of reward characteristics of conditioning stimuli can lead to a specific reductions in ‘attention' and or ‘sensory reaction' in frontal cortex and amygdala but not to general habituation to these stimuli or in other areas of the CNS.     

Are event-related potentials in multiple sclerosis indicative of cognitive impairment? Evoked and event-related potentials, psychometric testing and response speed: a controlled study.

Bimodal event-related potentials (ERPs), together with evoked potentials (EPs), measures of motor speed (tapping test, EMG latencies and reaction times (RT)), and psychometric test results were studied in a group of 30 multiple sclerosis (MS) patients and 19 controls. ERPs have been advocated as objective tests of cognitive function. In the present study ERPs were compared with the results of psychometric tests, which have a proven validity in measuring aspects of cognitive function that are important in daily life. Abnormal EMG, RT and tapping speed confirmed that motor aspects of performance were slowed in the MS group. In contrast, cognitive non-motor variables such as Raven-IQ and MQ were not significantly abnormal. The proportions of abnormal ERP N2 and P3 latencies did not differ between the groups. It is concluded that the slow performance of MS subjects is therefore most likely not due to cognitive speed decrement, but to motor, executive impairments. No significant relationships between ERP latencies and psychometric test results were found. This held even for a subgroup of 5 MS patients with psychometrically established cognitive impairments. Based on these results, we query the relevance of ERPs as subtle indicators of cognitive impairment in MS.     

Effect of umami taste stimulations on vagal efferent activity in the rat

Effects of umami taste stimulation with monosodium glutamate (MSG) on the efferent discharges in the pancreatic, gastric and hepatic branch of the vagus nerve were observed in the anesthetized rat, in comparison with those of sweet and salty taste stimulation. Umami taste stimulation with 2.8% MSG solution caused an enhancement of vagal activities in pancreatic, gastric and hepatic branches. Sweet taste stimulation with 5% glucose or 10% sucrose increased efferent activity of hepatic and pancreatic branches and inhibited in gastric branch of the vagus nerve. Salty taste stimulation with 5% NaCl resulted in an increase in vagal gastric nerve activity and a decrease in that of vagal pancreatic and hepatic nerve; however, weak salty taste stimulation with 0.9% NaCl solution caused no remarkable change in efferent activity. It was assumed that umami taste stimulation, strong salty taste stimulation and sweet taste stimulation revealed different patterns of vagal responses which play some role on different anticipatory changes in hepatic, pancreatic and gastric functions following ingestion of food with different taste.