Interference in short-term auditory memory

Although interference is a well-established forgetting function in short-term auditory memory, an adequate understanding of its underlying mechanisms and time course has yet to be attained. The present study therefore aimed to explore these issues in memory for timbre. Listeners compared standard and comparison complex tones, having distinct timbres (four components varying in frequency), over a 4.7-s retention interval and made a same–different response. This interval either was silent or included one of 15 distractor tones occurring 0 ms, 100 ms, or 1,200 ms after the standard. These distractors varied in the extent to which the frequencies of their component tones were shared with the standard. Performance in comparing the two tones was significantly impaired by distractors composed of novel frequencies, regardless of the temporal position at which the distractor occurred. These results were fully compatible with the recent timbre memory model (McKeown & Wellsted, 2009 McKeown, D. and Wellsted, D. 2009. Auditory memory for timbre. Journal of Experimental Psychology: Human Perception and Performance, 35: 855–875. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) and suggested that interference in auditory memory operates via a feature-overwriting mechanism.     

Auditory expectations for newly acquired structures

Our study investigated whether newly acquired auditory structure knowledge allows listeners to develop perceptual expectations for future events. For that aim, we introduced a new experimental approach that combines implicit learning and priming paradigms. Participants were first exposed to structured tone sequences without being told about the underlying artificial grammar. They then made speeded judgements on a perceptual feature of target tones in new sequences (i.e., in-tune/out-of-tune judgements). The target tones respected or violated the structure of the artificial grammar and were thus supposed to be expected or unexpected. In this priming task, grammatical tones were processed faster and more accurately than ungrammatical ones. This processing advantage was observed for an experimental group performing a memory task during the exposure phase, but was not observed for a control group, which was lacking the exposure phase (Experiment 1). It persisted when participants realized an in-tune/out-of-tune detection task during exposure (Experiment 2). This finding suggests that the acquisition of new structure knowledge not only influences grammaticality judgements on entire sequences (as previously shown in implicit learning research), but allows developing perceptual expectations that influence single event processing. It further promotes the priming paradigm as an implicit access to acquired artificial structure knowledge.     

Episodic retrieval processes take place automatically in auditory negative priming

Episodic retrieval processes involved in negative priming have been argued to be susceptible to the proportion of attended repetition trials. The more trials with the same prime and probe response, the more beneficial should it be to retrieve the prime episode, particularly its response. Retrieval of the prime episode, however, is task-inappropriate for ignored repetition trials, leading to negative priming. Correspondingly, visual negative priming increases with the proportion of attended repetition trials. We tested whether the same is true for the auditory modality. Three attended repetition proportion groups (0–25–50%) showed the same amount of negative priming. All groups committed more prime response errors in ignored repetition than in control trials, implying that prime response retrieval took place. Thus, retrieval processes in auditory negative priming appear to be automatic and cannot be influenced as easily as in the visual domain. In Experiment 2, the proportion of ignored repetition trials was manipulated (25–50–75%) to test whether auditory negative priming can be strategically manipulated at all. Similar to the visual modality negative priming was reduced with increasing proportion of ignored repetition trials. Differences between visual and auditory short-term memory are discussed to account for the results.     

The representation of pitch in auditory imagery: Evidence from S-R compatibility and distance effects

In three experiments we explored the nature of representations constructed during the perception and imagination of pitch. We employed a same–different task to eliminate the influence of nonauditory information and to minimise use of cognitive strategies on auditory imagery. A reference tone of frequency 1000, 1500, or 2000 Hz, or an imagined tone of a pitch indicated by a visual cue, was followed by a comparison tone (1000, 1500, or 2000 Hz) to which either a speeded same or different response was required. In separate experiments, same–different judgements were mapped to vertically (Experiments 1 and 2) and horizontally arranged responses (Experiment 3). Judgements of tones closer in pitch yielded longer reaction times and higher error rates than more distant tones, indicating a pitch distance effect for perceptual and imagery tasks alike. In addition, in the imagery task, same–different responses were faster when low-pitched tones demanded a bottom or left key response and high-pitched tones a top or right response than vice versa, suggesting that pitch is coded spatially. Together, these behavioural effects support the assumption that both perceived and imagined pitch are translated into an analogical representation in the spatial domain.     

Self-relevance increases the irrelevant sound effect: Attentional disruption by one's own name

Memory performance is severely disrupted when task-irrelevant sound is played during item presentation or in a retention interval. Working memory models make contrasting assumptions on whether the semantic content of the auditory distractors modulates the irrelevant sound effect. In the present study, participants made more errors in serial recall when they had to ignore sentences containing their own name as opposed to that of a yoked-control partner. These results are only consistent with working memory models that allow for attentional processes to play a role in the explanation of the irrelevant sound effect. With repeated presentation the disruptive effect of one's own name decreased, whereas the disruptive effect of the auditory distractors in the control condition remained constant. The latter finding is most consistent with the duplex model of auditory attention, which assumes that the irrelevant sound effect is primarily caused by automatic interference of acoustic distractor features, but at the same time allows for a disruption of encoding due to attentional capture by unexpected deviants. However, to explain the present results, the mechanism responsible for the attentional capture has to be extended to highly (self-)relevant auditory distractors.     

The other modality: Auditory stimuli in language switching

Language switching studies typically implement visual stimuli and visual language cues to trigger a concept and a language response, respectively. In the present study we set out to generalise this to another stimulus modality by investigating language switching with auditory stimuli next to visual stimuli. The results showed that switch costs can be obtained with both auditory and visual stimuli. Yet, switch costs were relatively larger with visual stimuli than with auditory stimuli. Both methodological and theoretical implications of these findings are discussed.     

The level of cholinergic nucleus basalis activation controls the specificity of auditory associative memory

Learning involves not only the establishment of memory per se, but also the specific details of its contents. In classical conditioning, the former concerns whether an association was learned while the latter discloses what was learned. The neural bases of associativity have been studied extensively while neural mechanisms of memory specificity have been neglected. Stimulation of the cholinergic nucleus basalis (NBs) paired with a preceding tone induces CS-specific associative memory. As different levels of acetylcholine may be released naturally during different learning situations, we asked whether the level of activation of the cholinergic neuromodulatory system can control the degree of detail that is encoded and retrieved. Adult male rats were tested pre- and post-training for behavioral responses (interruption of ongoing respiration) to tones of various frequencies (1-15 kHz, 70 dB, 2 s). Training consisted of 200 trials/day of tone (8.0 kHz, 70 dB, 2 s) either paired or unpaired with NBs (CS-NBs = 1.8 s) at moderate (65.7+/-9.0 microA, one day) or weak (46.7+/-12.1 microA, three training days) levels of stimulation, under conditions of controlled behavioral state (pre-trial stable respiration rate). Post-training (24 h) responses to tones revealed that moderate activation induced both associative and CS-specific behavioral memory, whereas weak activation produced associative memory lacking frequency specificity. The degree of memory specificity 24 h after training was positively correlated with the magnitude of CS-elicited increase in gamma activity within the EEG during training, but only in the moderate NBs group. Thus, a low level of acetylcholine released by the nucleus basalis during learning is sufficient to induce associativity whereas a higher level of release enables the storage of greater experiential detail. gamma waves, which are thought to reflect the coordinated activity of cortical cells, appear to index the encoding of CS detail. The findings demonstrate that the amount of detail in memory can be directly controlled by neural intervention.     

Auditory repetition priming is impaired in pure alexic patients

Alexia without agraphia, or "pure" alexia, is an acquired impairment in reading that leaves writing skills intact. Repetition priming for visually presented words is diminished in pure alexia. However, it is not possible to verify whether this priming deficit is modality-specific or modality independent because reading abilities are compromised. Hence, auditory repetition priming was assessed with lexical decision and word stem completion tasks in pure alexic patients with lesions in left inferior temporal-occipital cortex and the splenium. Perceptually based, modality-specific priming models predict intact auditory priming, since auditory association cortex is spared in the patients. Alternatively, modality-independent models, which suggest that priming reflects the temporary modification of an amodal system, might predict impairments. Baseline performance was matched in the patients and controls, although lexical decision priming measures showed an interaction between group and repetition lag. The patients showed intact immediate priming but significantly less priming than controls at longer delays. Furthermore, word stem completion priming was abolished in the patients. One explanation for the deficit is that left inferior temporal-occipital cortex supports amodal aspects of priming, as suggested by recent neuroimaging results. Another possibility is that long-term auditory priming relies on covert orthographic representations which were unavailable in the patients. The results provide support for interactive models of word identification.