Journal: The European journal of neuroscience
Music is a cultural universal and a rich part of the human experience. However, little is known about common brain systems that support the processing and integration of extended, naturalistic ‘real-world’ music stimuli. We examined this question by presenting extended excerpts of symphonic music, and two pseudomusical stimuli in which the temporal and spectral structure of the Natural Music condition were disrupted, to non-musician participants undergoing functional brain imaging and analysing synchronized spatiotemporal activity patterns between listeners. We found that music synchronizes brain responses across listeners in bilateral auditory midbrain and thalamus, primary auditory and auditory association cortex, right-lateralized structures in frontal and parietal cortex, and motor planning regions of the brain. These effects were greater for natural music compared to the pseudo-musical control conditions. Remarkably, inter-subject synchronization in the inferior colliculus and medial geniculate nucleus was also greater for the natural music condition, indicating that synchronization at these early stages of auditory processing is not simply driven by spectro-temporal features of the stimulus. Increased synchronization during music listening was also evident in a right-hemisphere fronto-parietal attention network and bilateral cortical regions involved in motor planning. While these brain structures have previously been implicated in various aspects of musical processing, our results are the first to show that these regions track structural elements of a musical stimulus over extended time periods lasting minutes. Our results show that a hierarchical distributed network is synchronized between individuals during the processing of extended musical sequences, and provide new insight into the temporal integration of complex and biologically salient auditory sequences.
Chemotherapy, especially if prolonged, disrupts attention, working memory and speed of processing in humans. Most cancer drugs that cross the blood-brain barrier also decrease adult neurogenesis. Because new neurons are generated in the hippocampus, this decrease may contribute to the deficits in working memory and related thought processes. The neurophysiological mechanisms that underlie these deficits are generally unknown. A possible mediator is hippocampal oscillatory activity within the theta range (3-12 Hz). Theta activity predicts and promotes efficient learning in healthy animals and humans. Here, we hypothesised that chemotherapy disrupts learning via decreases in hippocampal adult neurogenesis and theta activity. Temozolomide was administered to adult male Sprague-Dawley rats in a cyclic manner for several weeks. Treatment was followed by training with different types of eyeblink classical conditioning, a form of associative learning. Chemotherapy reduced both neurogenesis and endogenous theta activity, as well as disrupted learning and related theta-band responses to the conditioned stimulus. The detrimental effects of temozolomide only occurred after several weeks of treatment, and only on a task that requires the association of events across a temporal gap and not during training with temporally overlapping stimuli. Chemotherapy did not disrupt the memory for previously learned associations, a memory independent of (new neurons in) the hippocampus. In conclusion, prolonged systemic chemotherapy is associated with a decrease in hippocampal adult neurogenesis and theta activity that may explain the selective deficits in processes of learning that describe the ‘chemobrain’.
Synesthesia is a phenomenon in which an experience in one domain is accompanied by an involuntary secondary experience in another, unrelated domain; in classical synesthesia, these associations are arbitrary and idiosyncratic. Cross-modal correspondences refer to universal associations between seemingly unrelated sensory features, e.g., auditory pitch and visual size. Some argue that these phenomena form a continuum, with classical synesthesia being an exaggeration of universal cross-modal correspondences, whereas others contend that the two are quite different, since cross-modal correspondences are non-arbitrary, non-idiosyncratic, and do not involve secondary experiences. Here, we used the implicit association test to compare synesthetes' and non-synesthetes' sensitivity to cross-modal correspondences. We tested the associations between auditory pitch and visual elevation, auditory pitch and visual size, and sound-symbolic correspondences between auditory pseudowords and visual shapes. Synesthetes were more sensitive than non-synesthetes to cross-modal correspondences involving sound-symbolic, but not low-level sensory, associations. We conclude that synesthesia heightens universally experienced cross-modal correspondences, but only when these involve sound symbolism. This is only partly consistent with the idea of a continuum between synesthesia and cross-modal correspondences, but accords with the idea that synesthesia is a high-level, post-perceptual phenomenon, with spillover of the abilities of synesthetes into domains outside their synesthesias. To our knowledge, this is the first demonstration that synesthetes, relative to non-synesthetes, experience stronger cross-modal correspondences outside their synesthetic domains. This article is protected by copyright. All rights reserved.
The relation between informal musical activities at home and electrophysiological indices of neural auditory change detection was investigated in 2-3-year-old children. Auditory event-related potentials were recorded in a multi-feature paradigm that included frequency, duration, intensity, direction, gap deviants and attention-catching novel sounds. Correlations were calculated between these responses and the amount of musical activity at home (i.e. musical play by the child and parental singing) reported by the parents. A higher overall amount of informal musical activity was associated with larger P3as elicited by the gap and duration deviants, and smaller late discriminative negativity responses elicited by all deviant types. Furthermore, more musical activities were linked to smaller P3as elicited by the novel sounds, whereas more paternal singing was associated with smaller reorienting negativity responses to these sounds. These results imply heightened sensitivity to temporal acoustic changes, more mature auditory change detection, and less distractibility in children with more informal musical activities in their home environment. Our results highlight the significance of informal musical experiences in enhancing the development of highly important auditory abilities in early childhood.
Many neurons in the central auditory pathway, from the inferior colliculus (IC) to the auditory cortex (AC), respond less strongly to a commonly occurring stimulus than one that rarely occurs. The origin of this phenomenon, called stimulus-specific adaptation (SSA), remains uncertain. The AC sends descending projections to the IC that terminate most densely upon the dorsal, lateral and rostral IC cortices - areas where strong SSA has been reported. To investigate whether SSA in the IC is dependent upon the AC for its generation, we recorded the response from single IC neurons to stimuli presented in an oddball paradigm before, during and after reversibly deactivating the ipsilateral AC with a cryoloop. While changes in the basic response properties of the IC neurons were widespread (89%), changes in SSA sensitivity were less common; approximately half of the neurons recorded showed a significant change in SSA, while the other half remained unchanged. Changes in SSA could be in either direction: 18% enhanced their SSA sensitivity, while 34% showed reduced SSA sensitivity. For the majority of this latter group, cortical deactivation reduced, but did not eliminate, significant SSA levels. Only eight neurons seemed to inherit SSA from the AC, as their pre-existing significant level of SSA became non-significant during cortical deactivation. Thus, the presence of SSA in the IC is generally not dependent upon the corticocollicular projection, suggesting the AC is not essential for the generation of subcortical SSA; however, the AC may play a role in the modulation of subcortical SSA.
When we make hand movements to visual targets, gaze usually leads hand position by a series of saccades to task-relevant locations. Recent research suggests that the slow smooth pursuit eye movement system may interact with the saccadic system in complex tasks, suggesting that the smooth pursuit system can receive non-retinal input. We hypothesise that a combination of saccades and smooth pursuit guides the hand movements towards a goal in a complex environment, using an internal representation of future trajectories as input to the visuomotor system. This would imply that smooth pursuit leads hand position, which is remarkable, as the general idea is that smooth pursuit is driven by retinal slip. To test this hypothesis, we designed a video-game task in which human subjects used their thumbs to move two cursors to a common goal position while avoiding stationary obstacles. We found that gaze led the cursors by a series of saccades interleaved with ocular fixation or pursuit. Smooth pursuit was correlated with neither cursor position nor cursor velocity. We conclude that a combination of fast and slow eye movements, driven by an internal goal instead of a retinal goal, led the cursor movements, and that both saccades and pursuit are driven by an internal representation of future trajectories of the hand. The lead distance of gaze relative to the hand may reflect a compromise between exploring future hand (cursor) paths and verifying that the cursors move along the desired paths.
The unique role of the EEG alpha rhythm in different states of cortical activity is still debated. The main theories regarding alpha function posit either sensory processing or attention allocation as the main processes governing its modulation. Closing and opening eyes, a well-known manipulation of the alpha rhythm, could be regarded as attention allocation from inward to outward focus though during light is also accompanied by visual change. To disentangle the effects of attention allocation and sensory visual input on alpha modulation, 14 healthy subjects were asked to open and close their eyes during conditions of light and of complete darkness while simultaneous recordings of EEG and fMRI were acquired. Thus, during complete darkness the eyes-open condition is not related to visual input but only to attention allocation, allowing direct examination of its role in alpha modulation. A data-driven ridge regression classifier was applied to the EEG data in order to ascertain the contribution of the alpha rhythm to eyes-open/eyes-closed inference in both lighting conditions. Classifier results revealed significant alpha contribution during both light and dark conditions, suggesting that alpha rhythm modulation is closely linked to the change in the direction of attention regardless of the presence of visual sensory input. Furthermore, fMRI activation maps derived from an alpha modulation time-course during the complete darkness condition exhibited a right frontal cortical network associated with attention allocation. These findings support the importance of top-down processes such as attention allocation to alpha rhythm modulation, possibly as a prerequisite to its known bottom-up processing of sensory input.
In amphibians, the midbrain tectum is regarded as the visual centre for object recognition but the functional role of forebrain centres in visual information processing is less clear. In order to address this question, the dorsal thalamus was lesioned in the salamander Plethodon shermani, and the effects on orienting behaviour or on visual processing in the tectum were investigated. In a two-alternative-choice task, the average number of orienting responses toward one of two competing prey or simple configural stimuli was significantly decreased in lesioned animals compared to that of controls and sham-lesioned animals. When stimuli were presented during recording from tectal neurons, the number of spikes on presentation of a stimulus in the excitatory receptive field and a second salient stimulus in the surround was significantly reduced in controls and sham-lesioned salamanders compared to single presentation of the stimulus in the excitatory receptive field, while this inhibitory effect on the number of spikes of tectal neurons was absent in thalamus-lesioned animals. In amphibians, the dorsal thalamus is part of the second visual pathway which extends from the tectum via the thalamus to the telencephalon. A feedback loop to the tectum is assumed to modulate visual processing in the tectum and to ensure orienting behaviour toward visual objects. It is concluded that the tectum-thalamus-telencephalon pathway contributes to the recognition and evaluation of objects and enables spatial attention in object selection. This attentional system in amphibians resembles that found in mammals and illustrates the essential role of attention for goal-directed visuomotor action.
The aim is to evaluate how language experience (Chinese, English) shapes processing of pitch contours as reflected in the amplitude of cortical pitch response components. Responses were elicited from three dynamic curvilinear nonspeech stimuli varying in pitch direction and location of peak acceleration: Mandarin lexical Tone 2 (rising) and Tone 4 (falling), and a flipped variant of Tone 2, Tone 2' (nonnative). At temporal sites (T7/T8), Chinese listeners' Na-Pb response amplitudes to Tones 2 and 4 were greater than those of English listeners in the right hemisphere only; a rightward asymmetry for Tones 2 and 4 was restricted to the Chinese group. In common to both Fz-to-linked T7/T8 and T7/T8 electrode sites, the stimulus pattern (Tones 2 and 4 > Tone 2') was found in the Chinese group only. As reflected by Pb-Nb at Fz, Chinese subjects' amplitudes were larger than those of English subjects in response to Tones 2 and 4, and Tones 2 and 4 were larger than Tone 2', whereas for English subjects, Tone 2 was larger than Tone 2' and Tone 4. At frontal electrode sites (F3/F4), regardless of component or hemisphere, Chinese subjects' responses were larger in amplitude than those of English subjects across stimuli. For either group, responses to Tones 2 and 4 were larger than Tone 2'. No hemispheric asymmetry was observed at the frontal electrode sites. These findings demonstrate that cortical pitch response components are differentially modulated by experience-dependent, temporally distinct but functionally overlapping, weighting of sensory and extrasensory effects on pitch processing of lexical tones in the right temporal lobe and, more broadly, are consistent with a distributed hierarchical predictive coding process.
The testing of cognitive enhancers could benefit from the development of novel behavioural tasks that display better translational relevance for daily memory, and permit the examination of potential targets in a within-subjects manner with less variability. We here outline an optimized spatial ‘everyday memory’ task. We calibrate it systematically by interrogating certain well-established determinants of memory, and consider its potential for revealing novel features of encoding-related gene activation. Rats were trained in an event arena in which food was hidden in sandwells in a different location everyday. They found the food during an initial memory-encoding trial and were then required to remember the location in 6-alternative choice- or probe trials at various time-points later. Training continued daily over a period of 4 months, realising a stable high level of performance and characterised by delay-dependent forgetting over 24 h. Spaced but not massed access to multiple rewards enhanced the persistence of memory, as did post-encoding administration of the PDE4 inhibitor Rolipram. Quantitative PCR and then genome wide-analysis of gene-expression led to a new observation - stronger gene-activation in hippocampus and retrosplenial cortex following spaced than massed training. In a subsidiary study, a separate group of animals replicated aspects of this training profile, going on to show enhanced memory when training was subject to post-encoding environmental novelty. Distinctive features of this protocol include its potential validity as a model of memory encoding used routinely by human subjects everyday, and the possibility of multiple within-subject comparisons to speed up assays of novel compounds. This article is protected by copyright. All rights reserved.