The effects of attention and context on the spatial and magnitude components of the early responses of the event-related potential elicited by a rare stimulus

Visual reflexive attention as a useful measure of development

Cognitive psychology began over three-quarters of a century ago and we have learned a great deal in that time, including concerning the development of cognitive abilities such as perception, attention, and memory, all of which develop across infancy and childhood. Attention is one aspect of cognition that is vital to success in a variety of life activities and, arguably, the foundation of memory, learning, problem solving, decision making, and other cognitive activities. The cognitive abilities of later childhood and adulthood generally appear to depend on the reflexes, abilities, and skills of infancy. Research in developmental cognitive science can help us understand adult cognition and know when to intervene when cognitive function is at risk. This area of research can be challenging because, even in typical development, the course of cognitive development for a particular child does not always improve monotonically. In addition, the typical trajectory of this development has been understood differently from different historical perspectives. Neither the history of thought that has led to our current understanding of attention (including its various types) nor the importance of developmental aspects of attention are frequently covered in training early career researchers, especially those whose primary area of research in not attention. My goal is to provide a review that will be useful especially to those new to research in the subfield of attention. Sustained attention in adults and children has been well-studied, but a review of the history of thought on the development of reflexive attention with a focus on infancy is overdue. Therefore, I draw primarily on historical and modern literature and clarify confusing terminology as it has been used over time. I conclude with examples of how cognitive development research can contribute to scientific and applied progress.

Correctness and response time distributions in the MemTrax continuous recognition task: Analysis of strategies and a reverse-exponential model

A critical issue in addressing medical conditions is measurement. Memory measurement is difficult, especially episodic memory, which is disrupted by many conditions. On-line computer testing can precisely measure and assess several memory functions. This study analyzed memory performances from a large group of anonymous, on-line participants using a continuous recognition task (CRT) implemented at https://memtrax.com. These analyses estimated ranges of acceptable performance and average response time (RT). For 344,165 presumed unique individuals completing the CRT a total of 602,272 times, data were stored on a server, including each correct response (HIT), Correct Rejection, and RT to the thousandth of a second. Responses were analyzed, distributions and relationships of these parameters were ascertained, and mean RTs were determined for each participant across the population. From 322,996 valid first tests, analysis of correctness showed that 63% of these tests achieved at least 45 correct (90%), 92% scored at or above 40 correct (80%), and 3% scored 35 correct (70%) or less. The distribution of RTs was skewed with 1% faster than 0.62 s, a median at 0.890 s, and 1% slower than 1.57 s. The RT distribution was best explained by a novel model, the reverse-exponential (RevEx) function. Increased RT speed was most closely associated with increased HIT accuracy. The MemTrax on-line memory test readily provides valid and reliable metrics for assessing individual episodic memory function that could have practical clinical utility for precise assessment of memory dysfunction in many conditions, including improvement or deterioration over time.

Micro-analysis of infant looking in a naturalistic social setting: insights from biologically based models of attention

A current theory of attention posits that several micro-indices of attentional vigilance are dependent on activation of the locus coeruleus, a brainstem nucleus that regulates cortical norepinephrine activity (Aston-Jones et al., 1999). This theory may account for many findings in the infant literature, while highlighting important new areas for research and theory on infant attention. We examined the visual behaviors of n = 16 infants (6-7 months) while they attended to multiple spatially distributed targets in a naturalistic environment. We coded four measures of attentional vigilance, adapted from studies of norepinergic modulation of animal attention: rate of fixations, duration of fixations, latency to reorientation, and target 'hits'. These measures showed a high degree of coherence in individual infants, in parallel with findings from animal studies. Results also suggest that less vigilant infants showed greater habituation to the trial structure and more attentiveness to less salient stimuli during periods of high attentional competition. This pattern of results is predicted by the Aston-Jones model of attention, but could not be explained by the standard information processing model.

Towards neurophysiological assessment of phonemic discrimination: context effects of the mismatch negativity

OBJECTIVE

This study focusses on the optimal paradigm for simultaneous assessment of auditory and phonemic discrimination in clinical populations. We investigated (a) whether pitch and phonemic deviants presented together in one sequence are able to elicit mismatch negativities (MMNs) in healthy adults and (b) whether MMN elicited by a change in pitch is modulated by the presence of the phonemic deviants.

METHODS

Standard stimuli [i] were intermixed with small, medium or large pitch deviants or with pitch deviants of the same magnitude together with small and large phonemic deviants, [y] and [u], respectively.

RESULTS

When pitch and phonemic deviants were presented together, only the large pitch and phonemic contrasts elicited significant MMNs. When only pitch deviants were presented, the medium and large pitch contrasts elicited significant MMNs. The MMNs, in response to the medium and large pitch contrasts, were of similar magnitude across the two contexts.

CONCLUSIONS

Pitch and phonemic deviants can be tested together provided the pitch contrast is relatively large.

SIGNIFICANCE

A combined neurophysiological test of phonemic and pitch discrimination, as measured by the MMN, is a time-effective tool that may provide valuable information about the underlying cause of poorly specified phonemic representations in clinical populations.

Sedation modulates recognition of novel stimuli and adaptation to regular stimuli in critically ill adults

BACKGROUND

Responsiveness of critically ill patients is affected by disease and by therapy. Subjective tests of responsiveness (e.g., modified Ramsay score) reflect global integrity of a response arc that includes transduction, perception, classification, and an overt response. The performance of individual components is usually not assessed.

OBJECTIVE

To determine whether an association exists among sedative medications and the brain's component information processing and adaptive abilities.

DESIGN

Initial observational study of a convenience sample.

SETTING

A surgical intensive care unit of a university hospital.

PATIENTS

A total of 22 endotracheally intubated, mechanically ventilated patients chemically sedated with narcotics and a benzodiazepine (n = 12), or narcotics and propofol (n = 10) using sedation protocols.

INTERVENTIONS

None.

MEASUREMENTS AND FINDINGS

Patients were presented flashes of light and pulses of sound at fixed or random intervals. Patients receiving low doses of fentanyl and propofol adapted to stimuli presented at fixed intervals and retained the response to novelty. Patients receiving higher doses of those medications did not respond to novelty and responded to stimuli presented at fixed intervals as if they were novel. Patients receiving fentanyl and benzodiazepines had generally weaker responses to all stimuli. Moreover, their responses to fixed and random stimuli were similar. At low doses, the patients retained responses to novelty and adapted to fixed, whereas at higher doses the opposite was observed: the response to novelty was lost and the patients responded to fixed stimuli as if they were novel. These observations suggest that the sedative medications generally accelerate the physiologic decay of stimuli as they engage the brain's information processing and adaptive abilities and further suggest that different sedative medications may have different effects on the brain.

CONCLUSIONS

Commonly administered sedative medications may alter the brain's biophysical state and thereby modulate specific aspects of the brain's information processing and adaptive functions. These functions can be interrogated even when the patient is seemingly unresponsive. If this observation is confirmed in subsequent prospective controlled randomized trials, electrophysiologic interrogation of the brain's information processing and adaptive capacities could serve as an adjunct to clinical assessment of responsiveness and management of sedative medications.

Using event-related potentials to examine pharmacological effects on intervening cognitive functions in rats

Assessing toxicological and pharmacological effects on cognition using sensory evoked potentials and purposive behaviors as endpoints may limit testing to afferent activity and to populations able to follow directions. The present study uses a non-invasive method that does not require training or response to instruction to measure the brain's longer latency intervening cognitive response to stimulation. The averaged electrophysiological responses of 8 rat brains, Event-Related Potentials (ERPs), were recorded in 3 spatial dimensions and time while they experienced two time varying modes of auditory stimulation and anesthesia. Results show that both modes of stimulation elicited ERPs with similar magnitudes and latencies but with different electrophysiological patterns at each level of anesthesia. These results suggest anesthesia may not effect the brain's ability to detect and represent an input, but rather its ability to inhibit that input's decay over time so it can consolidate into a form able to benefit future processing. Anesthesia effected these events during the two modes of stimulation differently over time, suggesting this method of stimulation and recording may provide dependent variables sensitive to the brain's response at different dose levels.

Tri-axial recording of event-related potentials during passive cognitive tasks in patients with Alzheimer's disease

Standard methods used to assess cognitive function in patients with Alzheimer's Disease (AD) often use instructions to direct attention and gauge task difficulty, and measure only the output of processing, i.e., the patient's behavioral response. Because this may focus assessment on functions that are observable and to periods when patient comprehension is not compromised, the present study presented stimuli without instruction, manipulated task difficulty by varying stimulus factors, and used the brain's electrical response as the dependent variable. Because the recording electrode's position on the scalp may limit full examination of the voltage distribution of these responses, a Tri-Axial method of recording electrical activity within a Cartesian coordinate system was used. Results suggest attention may inhibit habituation so that inputs can be represented, discriminated and consolidated. For the control group, the levels of task difficulty modulated electrical peaks presumed to reflect the brain's ability to perform these functions. In the AD group, these responses were attenuated or absent, suggesting that dysfunctional attentional processing may underlie response errors often attributed to memory.