Psychopathy and Selective Attention During Performance of a Complex Perceptual-Motor Task

Autonomic and electrocortical activity were recorded while prison inmates with high (H) and low (L) ratings of psychopathy were presented with a series of binaural tone pips, either by themselves (passive attention) or while video games were being played (selective attention). During selective attention the subjects were told that the tone pips were irrelevant to the primary task, the video games. The N100 component of the auditory evoked potential was used as an index of attention paid to the tone pips, while performance on the video games was considered to be a reflection of attentiveness to the primary task. There were no group differences in N100 amplitude or latency during passive attention, supporting the results from several previous studies. During selective attention Group H gave small N100 responses to the tone pips during each video game trial, including the first one, while Group L gave large N100 responses to the tone pips during the first trial, and small responses during later trials. Both groups performed equally well during the first few trials, but while the performance of Group L continued to improve, that of Group H deteriorated over the last few trials. The results were interpreted in terms of limited capacity models of attention, and provided some support for the hypothesis that psychopaths allocate a relatively large proportion of their attentional resources to things of immediate interest, effectively ignoring other stimuli.     

Dose-dependent influences on electrophysiological signs of attention in humans after neuropeptide ACTH 4–10

Summary The afferent humoral system exerts significant influences on brain activity. Central nervous actions of the adrenocorticotropic hormone (ACTH) are most likely to be mediated by information coded in a portion of this hormone structure corresponding to ACTH 4–10. Our previous research suggested an impairing effect of ACTH 4–10 on electrophysiological signs of selective attention in humans. The present experiments in 12 male subjects investigated the influences of ACTH 4–10 on different aspects of attention as indicated by auditory event-related potential (AERP) components. Furthermore, doseresponse characteristics of these influences should be examined. Attention performance was tested in a dichotic listening paradigm, after 0, 0.1, 1.0, and 10 mg ACTH 4–10, administered intravenously 1 h prior to testing according to a double-blind latinsquare design. Different aspects of attention were measured by brain electrical responses evoked either by frequent standard or rare target tone pips, which the subject had to attend to, or to ignore. The selective type of attention was reflected by the Nd determined as mean difference in amplitude between AERPs to tone pips when attended and when unattended, for a latency range between 0–460 ms post-stimulus. In addition, plasma cortisol, heart rate, blood pressure, and behavioral performance were measured. Results indicated a clear reduction of the Nd amplitude after all doses of ACTH 4–10. Other indicators of attention mechanisms such as mismatch processing were not affected by the peptide. The diminished Nd after ACTH 4–10 was due to an increased processing of unattended stimuli, but simultaneously attended tones were processed less intensively. The effect of ACTH 4–10 on the Nd increased in strength with increasing doses applied. The demonstration of a linear dose-dependence of actions on the Nd supports a physiological significance for the actions of the neuropeptide ACTH 4–10 on attention.     

Event-related potentials and selective attention in major depressive illness.

Depressive episodes have been frequently characterized by deficits in information processing efficiency which are particularly evident when required to sustain or focus attention. As cerebral event-related potentials (ERPs) have been shown to reflect various aspects of selective attention and attentional dysfunction, this study attempted to examine ERPs in depressed patients performing a selective auditory attention task. Twenty-nine patients with a diagnosis of major depressive disorder (DSM-III) and 15 normal, non-psychiatric controls served as experimental subjects. Auditory potentials were recorded from the vertex of subjects who listened selectively to a series of tone pips in one ear and ignored concurrent tone pips to the other ear. Tone pips were delivered at short (320-500 ms) interstimulus intervals and subjects were required to detect, within the attended ear, rare 'target' tones of a different pitch than the more frequent 'standard' tones. In addition to behavioral indices of 'hits' and 'false alarms', ERP-derived measures included N1 amplitudes to attended and ignored stimuli, 'coefficients of attention' as calculated from N1 amplitude ratios and the latency onset and amplitude of the 'negative difference' (Nd) wave resulting from the subtraction of attended and ignored waveforms. Behavioral measures indicated that depressed patients were as efficient as controls in task performance and in fact they exhibited a significant left ear advantage in the additional task. Although a significant 'N1 effect' was observed with attended tones eliciting larger amplitudes than unattended tones, ERP measures of selective attention did not tend to differentiate the two groups.     

Developmental change in auditory selective attention as reflected by phasic heart rate changes

Heart rate was recorded from five different groups of children (ages 7, 10, 12, 14, and 20 years) while they were performing an auditory selective attention task. The participants were instructed to count rare tone pips embedded in a series of standard tone pips presented at one (attended) ear while ignoring rare and standard stimuli presented at the other (unattended) ear. A pattern of anticipatory heart rate deceleration followed by acceleration was associated with rare tone pips at the attended ear but not with rare tone pips that should be ignored. The absence of differential sensitivity of heart rate responses to rare tone pips presented at the unattended ear was observed for all age groups. These findings were interpreted to suggest that the ability to ignore irrelevant target stimuli has reached mature levels during middle childhood. The depth of anticipatory deceleration increased until age 14, suggesting that the ability to maintain attentional set continues to develop beyond childhood.     

Human Auditory Attention: The Olivocochlear Bundle May Function as a Peripheral Filter

Two experiments examined whether focused attention toward a visual display would alter the sensory transmission properties of the human auditory nerve and brainstem centers to irrelevant auditory tone pips. In the first experiment, 16 subjects either listened to 1000 Hz, 50dB SL tone pips presented binaurally at 10/sec (“Listen”), or mentally counted letters flashed rapidly on a screen (“Look”). The auditory brainstem potentials recorded from the vertex were averaged on-line in groups of 500 with a 10-msec sweep and a bandpass of 150–1500 Hz. Results indicated that during the “Look” trials, Wave 5 generated from the inferior colliculus (7.322 msec latency) was significantly reduced in amplitude by 16.4% and increased in latency by 27 μsec. A second experiment with 8 subjects demonstrated that the effects of attention are limited to the auditory nerve component when using 8000 Hz stimuli but are significant for both the auditory nerve and collicular components when a mid-frequency (2000 Hz) tone pip is used. These results suggest that during concentrated attention toward visual stimuli, irrelevant auditory stimuli may be attenuated at a peripheral level possibly through the action of the efferent olivocochlear bundle.     

The influence of a vasopressin-analogue (DGAVP) on event-related potentials in a stimulus-mismatch paradigm

To assess the influence of DGAVP (des-glycinamide-arginine-8-vasopressin, a synthetic vasopressin analogue) on the processing of stimuli and stimulus deviance in humans in a double-blind cross-over experiment, 13 subjects received 60 IU DGAVP versus placebo intranasally 48, 24, and 1 h prior to the experimental session. Auditory event-related potentials (ERPs) were taken as a tool to investigate central nervous processing in an experimental task that required the subjects to count different kinds of rare tone pips deviating in pitch and probability compared to frequent standard tones. Direction of attention was manipulated by instructing the subject to count a different class of deviating tone pips in each attention condition. DGAVP enhanced the N2 of the ERP to tone pips deviating extremely in pitch from standard tones, whether or not the extremely deviating pips were to be attended to by the subjects. This influence suggests an intensified mismatch processing under DGAVP that may result from a general excitatory effect of this substance on cortical activity.     

A waveform dissimilarity of auditory evoked potentials induced by the stimulation of meaningful nouns

Hemispheric asymmetry in language processing was investigated using an auditory evoked potential as the index for neurophysiological activity. Subjects were given the task of recognizing and classifying typical Japanese nouns, responding to nonsense syllables and responding to tone pips. Fourteen subjects participated and the AEPs of 12 subjects from the frontal, central and parietal regions were adopted for subsequent analyses. Correlation coefficients between the right/left AEPs from homologous scalp regions and a waveform similarity curve analysis that can indicate the similarity of two AEPs segmentally and successively, were adopted to provide the intra-individual symmetry index. Results were as follows: (1) The waveforms between the right/left AEPs induced by meaningful nouns were significantly dissimilar than those induced by nonsense syllables and tone pips; (2) the dissimilarities occurred mainly at 160 msec and 350 msec from the onset of the first syllable on the frontal and central regions. These findings may reflect the hemispheric asymmetry of neurophysiological activity in language processing.     

Does the heart know what the ears hear? A heart rate analysis of auditory selective attention

Between- and within-channel auditory selective attention were examined by presenting subjects with tone pips randomly to opposite ears; some pips had a slightly different pitch. Subjects were instructed to count rare, deviant tone pips at one ear and ignore all input to the other ear. Heart rate was sampled twice: once for the attended tone pips and once for the nonattended stimulus series. Heart rate responded differently to attended tone pips. While subjects were waiting for the rare stimulus to occur, heart rate slowed until the deviant stimulus was detected, which was followed by heart rate acceleration. Anticipatory heart rate deceleration was largely absent for nonatended series, and rare tone pips presented at the nonattended ear were not followed by acceleratory recovery. All tone pips elicited cardiac cycle time effects, that is, stimuli presented at short delays after the R wave prolonged the concurrent interbeat interval more than stimuli presented later. The cardiac cycle time effect was not altered by stimulus relevance (attended vs. nonattended) or significance (standard vs. rare). These results suggest that all stimuli receive preliminary perceptual analysis, but only attended stimuli are processed for further evaluation.     

Auditory Evoked Potential in Stage 2 and REM Sleep During a 30-Day Exposure to Tone Pulses

Ten subjects were exposed to 3.5K Hz tone pulses of 660 msec duration, presented 24-hr-per-day for 30 days. The interstimulus interval was 22 sec. There were 10 days each at 80, 85, and 90 dB in that order. The average evoked potential (AEP) at C₃ referenced to linked mastoids was obtained from contiguous stage 2 and REM sleep segments on the first, second, and last recorded nights of tone-pulse exposure. The AEP was consistently larger in stage 2 than in REM sleep. In both stage 2 and REM sleep, AEP amplitude on the second recorded night bore no consistent relationship to first or last recorded night AEPs. Only the N2–P3 amplitude yielded consistent decreases, with 9 of 10 subjects in both stage 2 and REM sleep having smaller N2–P3 amplitudes on the last than on the first recorded night. There were no changes in latency of any component. During sleep there is little, if any, habituation of the auditory AEP during long-duration exposures to nonmeaningful stimuli, and certainly no extinction of the AEP under these conditions.     

Single-trial latency variability of auditory evoked potentials may indicate immediate memory in the albino rat.

Fast habituation (FH) is defined as a decrease in auditory evoked potential (AEP) amplitude in response to the second of a pair of temporally juxtaposed (e.g. 1-s) tones. The degree of FH may depend, in part, on the subject's ability to anticipate the stimulus sequence. This paradigm has been used in our laboratory to study cognitive functioning in human subjects. We have also developed an animal model to investigate, more comprehensively, the anatomical and physiological basis of this phenomenon seen in human subjects. In the present investigation, we wished to determine the relationship between single-trial latency variability and AEP amplitude for two conditions: one for which FH is known to occur and one for which it is not present, due to the length of the interstimulus interval (ISI). Here AEPs were obtained to 40 pairs of 100-ms pure tone stimuli (70-dB SPL, 1- and 5-s ISI, 10-s interpair interval) from 19 chronically implanted, unanesthetized, restrained male Sprague-Dawley rats. The AEP latencies, amplitudes, and the single-trial latency variabilities were obtained for each component (P1, N1, P2 and N2). Findings indicated that FH was present for the 1-s ISI condition but not for the 5-s ISI condition. In addition, single-trial latency variability was negatively correlated with both Tones 1 and 2 AEP amplitudes in the 5-s ISI condition but only with Tone 1 amplitude in the 1-s ISI condition. Thus, single-trial latency variability predicted AEP amplitude only when FH did not occur. These results support earlier findings reported from our laboratory suggesting that the decrease in amplitude during FH is not related to increased variability in the time domain but rather to decreased neuronal output.     

Emotionally negative pictures increase attention to a subsequent auditory stimulus

Emotionally negative stimuli serve as a mechanism of biological preparedness to enhance attention. We hypothesized that emotionally negative stimuli would also serve as motivational priming to increase attention resources for subsequent stimuli. To that end, we tested 11 participants in a dual sensory modality task, wherein emotionally negative pictures were contrasted with emotionally neutral pictures and each picture was followed 600 ms later by a tone in an auditory oddball paradigm. Each trial began with a picture displayed for 200 ms; half of the trials began with an emotionally negative picture and half of the trials began with an emotionally neutral picture; 600 ms following picture presentation, the participants heard either an oddball tone or a standard tone. At the end of each trial (picture followed by tone), the participants categorized, with a button press, the picture and tone combination. As expected, and consistent with previous studies, we found an enhanced visual late positive potential (latency range = 300-700 ms) to the negative picture stimuli. We further found that compared to neutral pictures, negative pictures resulted in early attention and orienting effects to subsequent tones (measured through an enhanced N1 and N2) and sustained attention effects only to the subsequent oddball tones (measured through late processing negativity, latency range = 400-700 ms). Number pad responses to both the picture and tone category showed the shortest response latencies and greatest percentage of correct picture-tone categorization on the negative picture followed by oddball tone trials. Consistent with previous work on natural selective attention, our results support the idea that emotional stimuli can alter attention resource allocation. This finding has broad implications for human attention and performance as it specifically shows the conditions in which an emotionally negative stimulus can result in extended stimulus evaluation.     

Event-related potentials and selective attention to auditory stimuli varying in pitch and localization

Event-related potentials were recorded from subjects performing a discrimination task which required selective attention to one of (or divided attention to both of) two classes of tone pips imaged to arrive over two independent sound sources varying systematically in pitch and spatial localization. In selective attention N1 amplitude was larger and P2 amplitude was inversely smaller to the attended tones than to the unattended tones; P2 latency was prolonged to the attended tones; in divided attention, both N1 and P2 amplitudes and P2 latency were intermediate between selective attention and inattention. These attention effects upon both N1 and P2 components were interpreted to be due to a growth of a negative shift superimposed on those evoked components, rather than a modification of each component itself. This endogenous negativity was also considered to reflect the allocation of attentional capacity for discrimination processing whether tones coming from the attended source were ‘signal’ or not.     

Some effects of an ACTH 4-9 analog (Org 2766) on human performance.

The effects (on human beings) of the ACTH analog Org 2766 were investigated for a range of performance tests: complicated serial reaction task, running memory span, verbal learning and non-verbal mental ability tests (closure flexibility and non-verbal abstraction). Subjective ratings on feelings were taken and heart rate was measured. Only the 30-min reaction task produced significant drug effects. In this task performance tends to deteriorate as a function of time on task. During the test period there is a gradual increase in the number of lapses in performance due to moments of inattention. This deterioration is counteracted by the ACTH 4-9 analog, a result also found in previous study using ACTH 4-10 (Org OI63). Thus ACTH fragments which are devoid of endocrine effects seem to have a beneficial effect on goal-directed motivation oriented on the requirements of the task.     

Effects of Stimulation Rate and Attribute Cuing on Event-Related Potentials During Selective Auditory Attention

Auditory event-related potentials (ERPs) were recorded from subjects who attended selectively to a sequence of tones of one frequency and ignored a comparable sequence of tones having a different frequency and spatial origin. In one condition the tones consisted of randomized sequences of brief tone pips while in a second condition the tones were brief increments in intensity (pedestals) of continuous tones at the two frequencies. The tone pips and pedestals were delivered at comparable interstimulus intervals (ISIs), which were short (250–550 ms) in some runs and long (1250–2750 ms) in others. For both classes of stimuli, the subject's task was to detect occasional “target” tones of a slightly shorter duration than the more frequent “standard” tones. Stimuli of the attended frequency elicited a broad negative ERP component (Nd) relative to the unattended tone ERPs. The Nd wave had a considerably shorter onset latency and was smaller in overall amplitude at the faster rate of stimulation. However, the Nd wave did not differ in latency or amplitude between the tone pip and pedestal conditions at corresponding ISIs, suggesting that a high rate of information delivery is a more important factor in accelerating Nd onset than is the continuous reinforcement of the sensory cues that define the two classes of input.     

Asymmetrical auditory probe evoked potentials during REM and NREM sleep

Two experiments were conducted to evaluate interhemispheric differences in late auditory evoked potentials (AEPs) during rapid-eye-movement (REM), Stage 2, and Stage 4 sleep. In the first study, 1,000-Hz stimuli [80 db (SPL)] were presented binaurally at a rate of 1/1.1 s. Analyses of variance were computed on the absolute difference in the amplitude of right and left evoked responses. N1 AEPs were significantly more asymmetrical in Stage 4 sleep compared to either REM or Stage 2 sleep. A second study was conducted with a wider topographical electrode distribution. This study used both a long and a short interstimulus interval with 500-Hz 80-db SPL tone pips. The absolute difference in the amplitude of right and left AEPs was compared across sleep stage. Asymmetries were larger in Stage 4 sleep than in either REM or Stage 2. Examination of these data indicated relative hemispheric balance in REM and Stage 2 sleep with largest asymmetries in Stage 4. The results do not support the view that REM and non-REM sleep stages are associated with differential activation of the two cerebral hemispheres. Rather, they suggest that the sleep cycle is characterized by variations in the degree of asymmetry. Asymmetries in Stage 4 sleep were not consistently in favor of the left hemisphere.     

Vigilance and Human Attention Under Conditions of Methylphenidate and Secobarbital Intoxication: An Assessment Using Brain Potentials

Performance is known to fall-off with the time on a vigilance task. Treatment with methylphenidate attenuates this decrement while treatment with secobarbital enhances it. This experiment was designed to test whether this performance decrement and the drug effects on it are associated with changes in selective attention or in general state (i.e. motivation, alertness, or arousal). Subjects were treated with either 10 mg of methylphenidate, 100 mg of secobarbital, or a placebo in a double-blind cross-over design. Two event-related potentials (N₁ and P₃) were measured to four tone pips presented in a random sequence. Only two of the four tones could occur in each ear. The task during the vigil was to detect a designated target tone pip. The amplitude of N₁ was larger to both target and non-target stimuli in the attended ear than to those in the unattended ear; P₃ amplitude was larger only to the target stimuli. N₁ amplitude decreased with time especially when secobarbital was administered. This decrement in N₁ amplitude was comparable for both attended and unattended stimuli. The data support the view that the vigilance performance decrement and related drug effects on it are associated primarily with changes in general state.     

Single-neuron responses to rapidly presented temporal sequences in the primary auditory cortex of the awake macaque monkey

One fundamental process of the auditory system is to process rapidly occurring acoustic stimuli, which are fundamental components of complex stimuli such as animal vocalizations and human speech. Although the auditory cortex is known to subserve the perception of acoustic temporal events, relatively little is currently understood about how single neurons respond to such stimuli. We recorded the responses of single neurons in the primary auditory cortex of alert monkeys performing an auditory task. The stimuli consisted of four tone pips with equal duration and interpip interval, with the first and last pip of the sequence being near the characteristic frequency of the neuron under study. We manipulated the rate of presentation, the frequency of the middle two tone pips, and the order by which they were presented. Our results indicate that single cortical neurons are ineffective at responding to the individual tone pips of the sequence for pip durations of <12 ms, but did begin to respond synchronously to each pip of the sequence at 18-ms durations. In addition, roughly 40% of the neurons tested were able to discriminate the order that the two middle tone pips were presented in at durations of > or =24 ms. These data place the primate primary auditory cortex at an early processing stage of temporal rate discrimination.     

Metabotropic glutamate receptors subtype 5 are necessary for the enhancement of auditory evoked potentials in the lateral nucleus of the amygdala by tetanic stimulation of the auditory thalamus

The lateral nucleus of the amygdala (LA) receives axonal projections from the auditory thalamus, the medial geniculate nucleus (MGN), and mediates auditory fear conditioning. Tetanic electrical stimulation of the MGN can induce long-term potentiation of acoustically-evoked responses (AEPs) recorded in the LA of anesthetized rats. The present study investigated the temporal development of tetanus-induced AEP potentiation recorded in the LA of anesthetized rats during the recording time up to 120 min after tetanization. In addition, the present study investigated whether the artificially-induced AEP potentiation is mediated by the metabotropic glutamate receptors subtype 5 (mGluR5). The results show that AEPs recorded in the LA to a broadband-noise burst were significantly enhanced immediately after tetanic but not low-frequency stimulation of the MGN. The AEP potentiation was well retained up to 120 min after tetanization. High-dose (1.5 microg/4 microl) microinjection of the selective antagonist of mGluR5, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), into the ipsilateral lateral ventricle 30 min before tetanization completely blocked the AEP potentiation without affecting the baseline AEP. Low-dose (0.5 microg/4 microl) microinjection partially suppressed the AEP potentiation. When the high-dose MPEP was injected 40 min after tetanization, the AEP potentiation was not affected. These results indicate that in anesthetized rats mGluR5 receptors are necessary for the induction or early maintenance (40 min) of AEP potentiation in the LA by tetanic stimulation of the MGN.     

Auditory N1 as a change-related automatic response

To test the hypothesis that the N1 component of auditory evoked potentials (AEPs) is one form of the change-related response elicited by an abrupt change in sound pressure from a silent background, two AEP experiments were conducted. Change-N1 was evoked by a test stimulus at 70 dB following a 3-s conditioning stimulus of 0-69 dB. On-N1 was evoked by the test sound alone at various sound pressures. As the physical difference between stimuli increased, the amplitude of Change-N1 increased, and the latency shortened. The amplitude and latency of On-N1 showed a similar pattern to the Change-N1 response. These results support the idea that On-N1 is a change-related component elicited by a sound pressure change.     

Source localization of auditory evoked potentials after cochlear implantation

Little is known about how the auditory cortex adapts to artificial input as provided by a cochlear implant (CI). We report the case of a 71-year-old profoundly deaf man, who has successfully used a unilateral CI for 4 years. Independent component analysis (ICA) of 61-channel EEG recordings could separate CI-related artifacts from auditory-evoked potentials (AEPs), even though it was the perfectly time-locked CI stimulation that caused the AEPs. AEP dipole source localization revealed contralaterally larger amplitudes in the P1-N1 range, similar to normal hearing individuals. In contrast to normal hearing individuals, the man with the CI showed a 20-ms shorter N1 latency ipsilaterally. We conclude that ICA allows the detailed study of AEPs in CI users.