Individual Differences in Working Memory Capacity Modulate Electrophysiological Correlates of Semantic Negative Priming From Single Words

In the present study, event-related potentials (ERPs) were registered during a semantic negative priming (NP) task in participants with higher and lower working memory capacity (WMC). On each trial participants had to actively ignore a briefly presented single prime word, which was followed either immediately or after a delay by a mask. Thereafter, either a semantically related or an unrelated target word was presented, to which participants made a semantic categorization judgment. The ignored prime produced a behavioral semantic NP in delayed (but not in immediate) masking trials, and only for participants with a higher-WMC. Both masking type and WMC also modulated ERP priming effects. When the ignored prime was immediately followed by a mask (which impeded its conscious identification) a reliable N400 modulation was found irrespective of participants’ WMC. However, when the mask onset following the prime was delayed (thus allowing its conscious identification), an attenuation of a late positive ERP (LPC) was observed in related compared to unrelated trials, but only in the higher-WMC group showing reliable behavioral NP. The present findings demonstrate for the first time that individual differences in WMC modulate both behavioral measures and electrophysiological correlates of semantic NP.

Aragonite is calcite’s best friend at the seafloor

<p>Aragonite is about 50% more soluble than calcite in seawater and its pelagic production is dominated by pteropods. Moreover, it could account for a large fraction of marine CaCO<sub>3</sub> export. The <em>aragonite compensation depth</em> (ACD, the depth at which accumulation is balanced by dissolution) is generally very close to the <em>aragonite saturation depth</em>, i.e. within a few hundred metres. Conversely, the <em>calcite compensation depth</em> (CCD) can be 1-2 kilometres deeper than the <em>calcite saturation depth</em>. That aragonite disappears shallower than calcite in marine sediments is coherent with aragonite’s greater solubility, but why is the calcite <em>lysocline</em>, i.e. the distance between its compensation and saturation depths, much thicker than its aragonite equivalent?</p><p>Here, we suggest that at the seafloor, the addition of a soluble CaCO<sub>3</sub> phase (aragonite) results in the preservation of a predeposited stable CaCO<sub>3</sub> phase (calcite), and term this a negative priming action. In soil science, priming action refers to the increase in soil organic matter decomposition rate that follows the addition of fresh organic matter, supposedly resulting from a globally increased microbial activity (Bingeman et al., 1953). Using a new 3D model of CaCO<sub>3</sub> dissolution at the grain scale, we show that a conceptually similar phenomenon could occur at the seafloor, in which the dissolution of an aragonite pteropod at the sediment-water interface buffers the porewaters and causes the preservation of surrounding calcite. Since aragonite-producing organisms are particularly vulnerable to ocean acidification, we expect an increasing calcite to aragonite ratio in the CaCO<sub>3</sub> flux reaching the seafloor as we go further in the Anthropocene. This could, in turn, hinder the proposed aragonite negative priming action, and favour chemical erosion of calcite sediments.</p><p> </p><p>Reference: Bingeman, C.W., Varner, J.E., Martin, W.P., 1953. The Effect of the Addition of Organic Materials on the Decomposition of an Organic Soil. Soil Science Society of America Journal 17, 34-38.</p>

Identity-Based Crossmodal Negative Priming: Aftereffects of Ignoring in One Sensory Modality on Responding to Another Sensory Modality

Negative Priming (NP) refers to the phenomenon that responses towards previously ignored stimuli, as compared to new stimuli, are impaired. That is, NP is reflected in the performance on the probe display of a prime–probe sequence. NP is established in vision, audition and touch. In the current study, we presented participants with auditory, visual, and tactile manifestations of the same temporal patterns in order to measure NP across the senses. On each trial, the sensory modality shifted from the prime to the probe. Each prime and probe display consisted of a target and a distractor stimulus, presented to the same sensory modality. On some trials, the prime distractor repeated as probe target (ignored-repetition trials), on other trials the probe stimuli had not been involved in the prime display (control trials). We observed NP between audition and touch (Experiment 1) and between vision and audition (Experiment 2). These findings indicate that the processes underpinning NP can operate at an amodal, postperceptual level.