A wavelet packet model of evoked potentials

The standard methods for decomposition and analysis of evoked potentials are bandpass filtering, identification of peak amplitudes and latencies, and principal component analysis (PCA). We discuss the limitations of these and other approaches and introduce wavelet packet analysis. Then we propose the "single-channel wavelet packet model," a new approach in which a unique decomposition is achieved using prior time-frequency information and differences in the responses of the components to changes in experimental conditions. Orthogonal sets of wavelet packets allow a parsimonious time-frequency representation of the components. The method allows energy in some wavelet packets to be shared among two or more components, so the components are not necessarily orthogonal. The single-channel wavelet packet model and PCA both require constraints to achieve a unique decomposition. In PCA, however, the constraints are defined by mathematical convenience and may be unrealistic. In the single-channel wavelet packet model, the constraints are based on prior scientific knowledge. We give an application of the method to auditory evoked potentials recorded from cats. The good frequency resolution of wavelet packets allows us to separate superimposed components in these data. Our present approach yields estimates of component waveforms and the effects of experiment conditions on the amplitude of the components. We discuss future extensions that will provide confidence intervals and p values, allow for latency changes, and represent multichannel data.     

The On-Line Processing of Verb-Phrase Ellipsis in Aphasia

We investigate the on-line processing of verb-phrase ellipsis (VPE) constructions in two brain injured populations: Broca’s and Anomic aphasics. VPE constructions are built from two simple clauses; the first is the antecedent clause and the second is the ellipsis clause. The ellipsis clause is missing its verb and object (i.e., its verb phrase (VP)), which receives its reference from the fully specified VP in the antecedent clause. VPE constructions are unlike other sentence types that require displacement of an argument NP; these latter constructions (e.g., object-relatives, wh-questions) yield either on-time or delayed antecedent reactivation. Our results demonstrate that Anomics, like unimpaired individuals, evince reactivation of the direct object NP (within the VP) at the elided position. Broca’s patients, on the other hand, do not show reactivation of the antecedent. We consider several interpretations for our data, including explanations focusing on the larger ‘grain size’ of the reconstructed material in the ellipsis clause, the properties of the auxiliary that carries tense and agreement features, and the possibility that the cost-free syntactic copy procedure claimed to underlie VPE may be modulated by the functional deficit in Broca’s aphasia.     

The battle for Broca's region

The intense effort to characterize Broca's region has produced many views on its anatomy and function. Here, we present the leading approaches and consider ways to adjudicate among them empirically. Anatomically, we focus on the cytoarchitecture of Brodmann areas 44 and 45, which constitute Broca's region. Functionally, we discuss four views: action perception, working memory, syntactic complexity and syntactic movement. We compare these views, reflect on how they can be distinguished experimentally and review relevant aphasia and functional magnetic resonance imaging (fMRI) studies. Although no single hypothesis accounts for all of the data, the role of Broca's region in language comprehension is best explained by the syntactic movement account. This conclusion opens the door for an attempt to define general principles for the neural representation of linguistic knowledge.     

Neurolinguistics and neuroimaging: forward to the future,or is it back?

Books reviewed in this article:
Michael Gazzaniga (ed.), Cognitive Neuroscience: A Reader
Alec Marantz, Yasushi Miyashita, and Wayne O'Neil (ed.), Image, Language, Brain: Papers From the First Mind Articulation Project Symposium
Colin Brown and Peter Hagoort, The Neurocognition of Language     

Probing the Brain Substrates of Cognitive Processes Responsible for Context Effects on Recognition Memory

ABSTRACT

Context effects on episodic recognition memory involve separable contributions of target-context binding, additive familiarity, and configural constancy. Here we examine whether these factors reflect contributions of processes attributed to different brain substrates. First, we challenged frontal and medial temporal lobe-based cognitive capacities in healthy young adults, employing divided attention tasks at encoding and retrieval, and extended retrieval delay, respectively. Target-context binding effects were specifically attenuated by delay, but not by divided attention. In a second experiment, older adults were identified by neuropsychological testing as having different levels of frontal and medial temporal lobe-dependent cognitive functions. Consistent with Experiment 1, older adults with low medial temporal lobe function exhibited reduced target-context binding effects, but levels of frontal function did not modulate binding effects. These findings indicate that unlike source memory, context effects on memory are associated with the integrity of medial temporal lobe-based processes but not with the integrity of frontal lobe-based processes. Our findings also emphasize the importance of discriminating between functional subgroups in the attempt to characterize memory processes in older adults.     

The Applied Cognitive Psychology of Attention: A Step Closer to Understanding Magic Tricks

Drawing on psychological science, magic provides a unique perspective on applied cognition. Only sparse systematic research, however, documents the thought processes associated with viewing magic tricks. With responses from over 1000 participants, here, we show how individuals construe a classic magic routine wherein a performer appears to vanish a pen. Thirty‐four percent of participants correctly identified the key moment of the disappearance with only 11% thereof knowing what actions the magician actually performed to achieve the effect. Our collective findings support what magicians have known for a long time: knowing when a critical maneuver occurs hardly reveals the associated modus operandi. In line with a modern theory of attention, we discuss our results and highlight the interaction between the when and where attention modules as a necessary component of applied cognition in ecological settings. Copyright © 2012 John Wiley & Sons, Ltd.     

Physiological Reactions to a Suicide Film: Suicide Attempters,Suicide Ideators,and Nonsuicidal Patients

A film about two teenagers who commit suicide was shown to three groups of psychiatric inpatients: 17 who had attempted suicide, 20 who had expressed suicidal thoughts, and 10 who were not suicidal. Anxiety before and after the film was evaluated with psychometric (anxiety rating scale) and physiological tools (heart and respiration rate, blood pressure, electromyogram). Values noted before and after screening, and the degree of change in these values, were compared. In addition, psychomotor agitation was rated at several points during the film. Most results were negative. The suicide attempters had significantly lower postscreening heart rates and a significantly lesser change in heart and respiration rates than the other two groups. The suicide attempters revealed an increase in psychomotor agitation until the discovery of the suicide and a decrease thereafter, whereas the agitation of the nonsuicidal patients continued to increase from the start to the end of the film. The study suggests that on some parameters, suicide attempters reveal less anxiety than nonsuicidal psychiatric patients following exposure to a simulated suicide. The reaction of suicide ideators falls somewhere between the two groups.     

Child/Adolescent Abuse and Suicidal Behavior: Are They Sex Related?

The association between childhood and adolescent abuse and suicidal behavior, and the possible contribution of abuse to sex differences in non lethal suicidal behavior, was investigated. Data were extracted from the Israel‐based component of the WHO World Mental Health Survey (Kessler & Utsun, 2008a). Increased risk for ideation, plan, and suicidal attempt were associated with childhood abuse, and increased risk for attempt was associated also with abuse at adolescence. No associations with sex or sex by abuse interactions were observed. The higher frequency of childhood abuse among women could account in part for their higher rates of suicidal attempts as compared to men.