The N400 elicited by homonyms in puns: Two primes are not better than one

Abstract

To comprehend a pun involving a homonym (e.g., The prince with a bad tooth got a crown), both meanings of the homonym must be accessed and selected. Previous ERP studies have shown that the N400 reflects lexicosemantic processing, but none have directly investigated the N400 elicited by homonyms in the unique context of puns. Here, N400 priming effects showed that the dual context of puns (e.g., the primes prince and tooth) did not facilitate homonym processing in comparison to single dominant biasing (e.g., The prince with a bad leg got a crown) or subordinate biasing (e.g., The adult with a bad tooth got a crown) conditions. However, homonyms did elicit a less negative N400 (i.e., priming) in the pun condition in comparison to the neutral context condition (e.g., The adult with a bad leg got a crown). These findings are interpreted in terms of the dominant advantage and subordinate bias effect posited by the reordered access model of homonym processing, and in terms of N400 amplitude as an index of how consistently various sources of semantic featural information converge on one lexical item, even when two lexical items must be activated for comprehension.

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Don't startle me—Interference of startle probe presentations and intermittent ratings with fear acquisition

Abstract

Reproducibility is fundamental to science and a recent matter of discussion. We report challenges for conceptual replications when employing different readout measures to target the same theoretical construct, particularly those requiring probed reactions. This was addressed in a fear conditioning paradigm, a prototype of emotional learning, in three experimental groups (N_total = 57). We demonstrate that the inclusion of startle probes (95 dB burst of white noise) to elicit a startle reflex delays the acquisition of fear as reflected by skin conductance responses and intermittent fear ratings. The inclusion of fear ratings in turn did not significantly affect fear acquisition. Hence, subtle differences in experimental design, such as the inclusion of a single additional outcome measure, may substantially impact on study results and interpretations. Thus, small effects, as are common in between-group comparisons, may be particularly susceptible to this, which has strong implications for the replication of findings across studies employing slightly different experimental designs.

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Recollection is delayed under changed viewing conditions: A graded effect on the latency of the late posterior component

Abstract

Object recognition is a central human ability. In everyday life, the conditions under which objects have to be recognized are usually not perfect. Often, viewing conditions change in between two encounters with an object; typical are changes in illumination or in the object-observer distance. With such changes, object recognition sometimes feels slightly delayed. We examined this phenomenon empirically by measuring the latency of the well-established electrophysiological correlate of recollection, the late posterior component (LPC), in an object-recognition task. Although the cognitive processes underlying successful recognition are well examined, thus far the consequences of changed viewing conditions on the timing of these processes have not been investigated. The ERP technique is well suited for investigating this question, because it allows differentiating between processes contributing to recognition times (in particular, recollection from familiarity as indexed by the FN400 component) and measuring their time course with high temporal precision. In the present study, participants' task was to differentiate previously studied (old) objects from a set of new objects. Viewing conditions for old objects changed slightly, changed strongly, or remained identical between learning and test. We found that the latency of the LPC in response to an old object was delayed whenever viewing conditions changed. Moreover, this delay in LPC latency scaled with the size of the change. These effects were absent for the FN400. This is the first examination of effects of changes in viewing conditions on the latency of recollection and the first dissociation of FN400 and LPC latencies.

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'The Greatest' by Sia

The singer's latest music video is a tribute to the Orlando nightclub shooting victims.

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'The Greatest' by Sia

The singer's latest music video is a tribute to the Orlando nightclub shooting victims.

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Slow gamma rhythms in CA3 are entrained by slow gamma activity in the dentate gyrus

In hippocampal area CA1, slow (~25-55 Hz) and fast (~60-100 Hz) gamma rhythms are coupled with different CA1 afferents. CA1 slow gamma is coupled to inputs from CA3, and CA1 fast gamma is coupled to inputs from the medial entorhinal cortex (Colgin et al. 2009). CA3 gives rise to highly divergent associational projections, and it is possible that reverberating activity in these connections generates slow gamma rhythms in the hippocampus. However, hippocampal gamma is maximal upstream of CA3, in the dentate gyrus (DG) region (Bragin et al. 1995a). Thus, it is possible that slow gamma in CA3 is driven by inputs from DG. Yet, few studies have examined slow and fast gamma rhythms in DG recordings. Here, we investigated slow and fast gamma rhythms in paired recordings from DG and CA3 in freely moving rats in order to determine whether slow and fast gamma rhythms in CA3 are entrained by DG. We found that slow gamma rhythms, as opposed to fast gamma rhythms, were particularly prominent in DG. We investigated directional causal influences between DG and CA3 using Granger causality analysis and found that DG slow gamma influences CA3 slow gamma. Moreover, DG place cell spikes were strongly phase-locked to CA3 slow gamma rhythms, suggesting that DG excitatory projections to CA3 may underlie this directional influence. These results indicate that slow gamma rhythms do not originate in CA3 but rather that slow gamma activity upstream in DG entrains slow gamma rhythms in CA3.

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Botulinum toxin injection causes hyperreflexia and increased muscle stiffness of the triceps surae muscle in the rat.

Botulinum toxin is used to diminish spasticity and reduce the risk of development of contractures. Here, we investigated changes in muscle stiffness caused by reflex activity or elastic muscle properties following botulinum toxin injection in the triceps surae muscle in rats. Forty-four rats received injection of botulinum toxin in the left triceps surae muscle. Control measurements were performed on the non-injected contralateral side in all rats. Acute experiments were performed 1, 2, 4 and 8 weeks following injection. The triceps surae muscle was dissected free, the Achilles tendon was cut and attached to a muscle puller. The resistance of the muscle to stretches of different amplitudes and velocities was systematically investigated. Reflex mediated torque was normalized to the maximal muscle force (Mmax) evoked by supramaximal stimulation of the tibial nerve. Botulinum toxin injection caused severe atrophy of the triceps surae muscle at all time points. The force generated by stretch reflex activity was also strongly diminished, but not to the same extent as Mmax at 2 and 4 weeks, signifying a relative reflex hyperexcitability. Passive muscle stiffness was unaltered at 1 week, but increased at 2, 4 and 8 weeks (p<0.01). These data demonstrate that botulinum toxin causes a relative increase in reflex stiffness, which is likely caused by compensatory neuroplastic changes. The stiffness of elastic elements in the muscles also increased. The data are not consistent with the ideas that botulinum toxin is an efficient antispastic medication or that it may prevent development of contractures.

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