Temporal regularity effects on pre-attentive and attentive processing of deviance

Temporal regularity allows predicting the temporal locus of future information thereby potentially facilitating cognitive processing. We applied event-related brain potentials (ERPs) to investigate how temporal regularity impacts pre-attentive and attentive processing of deviance in the auditory modality. Participants listened to sequences of sinusoidal tones differing exclusively in pitch. The inter-stimulus interval (ISI) in these sequences was manipulated to convey either isochronous or random temporal structure. In the pre-attentive session, deviance processing was unaffected by the regularity manipulation as evidenced in three event-related-potentials (ERPs): mismatch negativity (MMN), P3a, and reorienting negativity (RON). In the attentive session, the P3b was smaller for deviant tones embedded in irregular temporal structure, while the N2b component remained unaffected. These findings confirm that temporal regularity can reinforce cognitive mechanisms associated with the attentive processing of deviance. Furthermore, they provide evidence for the dynamic allocation of attention in time and dissociable pre-attentive and attention-dependent temporal processing mechanisms

Neurophysiological alterations during phoneme and word processing in the acute stage of aphasia

Only a few studies have investigated neurophysiological substrates of phonological impairment in patients with aphasia (PWA) in the acute stage after stroke (Ilvonen et al., 2003; Nolfe et al., 2006). Behavioral evaluation is often problematic or even impossible in PWA in the acute stage, as some patients cannot be instructed due to severely impaired comprehension, reduced consciousness or confusion. Event-related potentials (ERPS) can circumvent such problems as they have already demonstrated their sensitivity and usefulness in measuring certain language processes in both a healthy and clinical population. The objective of the present study is to investigate neurophysiological substrates of phoneme and word processing in PWA with phonological disorders (PWA-PD) in the acute stage after stroke. Ten PWA-PD (5 men, 5 women; mean age 69.4 years +/- 3.46) are included and compared to 44 healthy control participants (HC) (20 men, 24 women; mean age 44.46 years +/- 13.76). All patients suffer from a first-ever stroke in the left hemisphere, are right-handed, have Dutch as native language and present with acute phonological disorders as established with the Psycholinguistic Assessment of Language Processing in Aphasia (Bastiaanse et al., 1995). PWA-PD admitted with a recurrent stroke, left handedness, indications for comorbid cognitive disorders and severe hearing deficits are excluded. Phoneme discrimination is studied in a pre-attentive (MMN) and attentive (P300) oddball task with respect to the phonemic contrasts place of articulation (PoA), voicing and manner of articulation (MoA) to explore whether a qualitative pattern of impaired phonemic contrast sensitivity can be determined. Word recognition is studied in a pre-attentive oddball task, which consists of differentiating real words from pseudowords. The electroencephalogram (EEG) is recorded through 23 Ag/AgCl-electrodes using a linked ears reference and an electrode placed on the forehead as ground. Further EEG analysis includes additional filtering, independent component analysis, segmentation, baseline correction and artifact rejection. Statistical analysis is performed on amplitudes and latencies specifically taking into account the large heterogeneity among PWA-PD. During phoneme discrimination, PWA-PD only show MMN amplitude reductions with voicing as phonemic contrast in the pre-attentive condition, whereas all three phonemic contrasts reveal smaller P300 amplitudes compared to HC in the attentive condition. PWA-PD show a larger response to PoA compared to MoA and voicing in the pre-attentive condition, whereas in the attentive condition only the difference between PoA and voicing remains. During word recognition, PWA-PD and HC display larger responses to pseudowords compared to real words from 100 ms onwards, continuing in the P200 and N400 time windows, despite the fact that responses to pseudowords show longer latencies in PWA-PD. In summary, this demonstrates a distinct pattern of impaired phonemic contrast sensitivity in PWA-PD, with PoA being the most resistant, voicing the most vulnerable and a substantial effect of attention. Moreover, PWA-PD suffer from a delay in lexical access due to a less efficient information transfer, which did not impair the response to pseudowords. For possible clinical implementation of ERPs, pre-attentive tasks seem to be more suitable than attentive tasks in the acute stage of aphasia

Attentive processing improves object recognition

The human visual system can recognize several thousand object categories irrespective of their position and size. This combination of selectivity and invariance is built up gradually across several stages of visual processing. However, the recognition of multiple objects in cluttered visual scenes presents a difficult problem for human as well as machine vision systems. The human visual system has evolved to perform two stages of visual processing: a pre-attentive parallel processing stage, in which the entire visual field is processed at once and a slow serial attentive processing stage, in which aregion of interest in an input image is selected for "specialized" analysis by an attentional spotlight. We argue that this strategy evolved to overcome the limitation of purely feed forward processing in the presence of clutter and crowding. Using a Bayesian model of attention along with a hierarchical model of feed forward recognition on a data set of real world images, we show that this two stage attentive processing can improve recognition in cluttered and crowded conditions

Towards a Unified Theory of Neocortex: Laminar Cortical Circuits for Vision and Cognition

A key goal of computational neuroscience is to link brain mechanisms to behavioral functions. The present article describes recent progress towards explaining how laminar neocortical circuits give rise to biological intelligence. These circuits embody two new and revolutionary computational paradigms: Complementary Computing and Laminar Computing. Circuit properties include a novel synthesis of feedforward and feedback processing, of digital and analog processing, and of pre-attentive and attentive processing. This synthesis clarifies the appeal of Bayesian approaches but has a far greater predictive range that naturally extends to self-organizing processes. Examples from vision and cognition are summarized. A LAMINART architecture unifies properties of visual development, learning, perceptual grouping, attention, and 3D vision. A key modeling theme is that the mechanisms which enable development and learning to occur in a stable way imply properties of adult behavior. It is noted how higher-order attentional constraints can influence multiple cortical regions, and how spatial and object attention work together to learn view-invariant object categories. In particular, a form-fitting spatial attentional shroud can allow an emerging view-invariant object category to remain active while multiple view categories are associated with it during sequences of saccadic eye movements. Finally, the chapter summarizes recent work on the LIST PARSE model of cognitive information processing by the laminar circuits of prefrontal cortex. LIST PARSE models the short-term storage of event sequences in working memory, their unitization through learning into sequence, or list, chunks, and their read-out in planned sequential performance that is under volitional control. LIST PARSE provides a laminar embodiment of Item and Order working memories, also called Competitive Queuing models, that have been supported by both psychophysical and neurobiological data. These examples show how variations of a common laminar cortical design can embody properties of visual and cognitive intelligence that seem, at least on the surface, to be mechanistically unrelated.National Science Foundation (SBE-0354378); Office of Naval Research (N00014-01-1-0624

Is neural and behavioral sound processing affected by practice strategies in musicians?

Previous exploratory studies suggest that pre-attentive auditory processing of musicians differ depending on the strategies they use in music practicing and performance. This study aimed at systematically determining whether there are differences in neural sound processing and behavioral measures between musicians preferring and not-preferring aural strategies including improvising, playing by ear and rehearsing by listening recordings. Participants were assigned into aural (n = 13) and non-aural (n = 11) groups according to how much they employ aural strategies, as determined by a questionnaire. The amplitude, latency, and scalp topography of the memory-related mismatch negativity (MMN) component of the event-related brain potentials were investigated with the so-called ‘optimal’ paradigm probing simple sound feature processing and with the ‘transposed-melody’ paradigm, probing complex sound pattern processing. Further, their behavioral accuracy in sound perception was tested with an attentive discrimination task in the transposed-melody paradigm and with the AMMA musicality test. Results showed that there were group differences both at the pre-attentive and behavioral levels of sound processing. First, in the optimal paradigm, the MMN morphology for the isolated sound features was similar between groups but its MMN amplitude, latency and topography for different sound features differed. Second, in the ‘transposed-melody’ paradigm, MMN was larger for the deviant that changed its contour as compared with the deviant that changed the last tone and thus the interval between the two last tones of the melody. The Contour-MMN amplitude as determined in the beginning of the recordings correlated with the subsequent behavioral discrimination accuracy in attentive condition. However, there were no group differences in the behavioral discrimination both deviants being detected equally well. The Interval-MMN amplitudes decreased especially in the aural group after the attentive condition. Moreover, the Interval-MMN latency in the non-aural group prolonged after the attentive condition as compared to the preceding condition whereas in the aural group the MMN latency shortened. No changes were seen in the Contour-MMN between conditions with either of the groups. Third, the non-aural group outperformed the aural group in the AMMA musicality test (Tonal subtest and Total scores). Additionally, AMMA scores (especially the Rhythm) correlated significantly with the Contour-MMN amplitudes after the attentive condition. Taken together, the present results suggest that practice strategies do not affect musicians' pre-attentive processing of simple sound features but might affect complex sound pattern processing. Complex sound pattern processing related also to the attentive behavioral performance in all musicians. While providing new insights into behavioral and neural differences between musicians preferring different practice strategies, results only partially support previous findings concerning discriminatory accuracy of violation within complex sound pattern learning.Aiempien tutkimusten mukaan muusikoiden käyttämät harjoittelustrategiat voivat vaikuttaa heidän esitietoiseen kuulotiedon käsittelyynsä. Tutkimuksen tavoitteena oli systemaattisesti selvittää, eroaako auraalisia ja ei-auraalisia (ts. korvakuuloon perustuvia) harjoittelustrategioita suosivien muusikoiden kuulotiedon käsittely aivotutkimusten ja behavioraalisten mittausten perusteella. Auraalisilla strategioilla tarkoitettiin harjoittelukäytäntöjä, jotka sisälsivät runsaasti improvisointia, korvakuulolta soittamista ja harjoittelua äänitteiden kuuntelun avulla. Osallistujat jaettiin auraaliseen (n=13) ja ei-auraaliseen (11) ryhmään sen perusteella kuinka paljon he kertoivat taustatietokyselylomakkeessa hyödyntävänsä auraalisia strategioita. Tutkimusmenetelminä käytettiin aivojen jännitevaste-rekisteröintejä (EEG:tä) poikkeavuusnegatiivisuusasetelmassa, AMMA-musikaalisuustestiä sekä tätä tutkimusta varten suunniteltua kyselylomaketta. EEG-kokeessa esitettiin yksinkertainen äänten piirteitä testaava optimiparadigma sekä monimutkaisten, transponoitujen, melodiakulkujen paradigma, jonka aikana testattiin myös kuulohavainnoinnin erottelutarkkuutta tarkkailutilanteessa. Erillisellä tutkimuskerralla tehtiin AMMA-musikaalisuustesti sekä täytettiin taustatietokyselylomake. Tulosten mukaan ryhmät erosivat toisistaan sekä esitietoisella että tietoisella kuulotiedonkäsittelyn tasolla. Optimiparadigmassa MMN ei eronnut amplitudin tai latenssin osalta ryhmien välillä, mutta sen amplitudi ja jakauma eri äänen poikkeamapiirteiden välillä vaihteli. Transponoitujen melodioiden paradigmassa MMN oli vahvempi kuviopoikkeavuudelle (jossa toiseksi viimeinen sävel vaihtui) verrattuna intervallipoikkeavuudelle (jossa viimeinen sävel vaihtui). Kuviopoikkeavuuden MMN ensimmäisessä ei-tarkkailutilanteessa korreloi merkitsevästi tarkkailutilanteen behavioraaliseen erottelutarkkuuteen. Sitä vastoin, behavioraalinen erottelutarkkuus ei eronnut ryhmien välillä ja molemmat poikkeavuudet eroteltiin yhtä tarkasti. Intervalli-MMN:n amplitudi pienentyi tarkkailutilanteen erityisesti auraalisella ryhmällä. Lisäksi intervalli-MMN:n latenssi kasvoi tarkkailutilanteen jälkeen ei-auraalisella ryhmällä, kun taas auraalisella ryhmällä se pieneni verrattuna tarkkailua edeltävään tilanteeseen. Kuvio-MMN ei eronnut tilanteiden välillä kummallakaan ryhmällä. AMMA-musikaalisuustestissä ei-auraalinen ryhmä suoriutui auraalista paremmin sävelkorkeuksien erottelukykyä testaavassa (’Tonal’) osiossa ja koko testissä. Lisäksi AMMA:n tulokset (erityisesti Rytmi-osio) korreloivat merkitsevästi tarkkailutilanteen jälkeiseen kuvio-MMN:n amplitudiin. Tulosten mukaan harjoittelustrategiat eivät näytä vaikuttavan muusikoiden esitietoiseen äänen piirteiden havaitsemiseen mutta saattavat vaikuttaa monimutkaisten melodiakulkujen havaitsemiseen. Monimutkaisten melodiakulkujen kuulotiedonkäsittely liittyi myös behavioraaliseen suoriutumiseen kaikilla muusikoilla. Tulokset tarjoavat uutta tietoa erilaisia harjoittelustrategioita suosivien muusikoiden välisistä eroista behavioraalisen ja neuraalisen tarkastelun tasoilla, mutta tukevat vain osittain aiempia aivotutkimuslöydöksiä poikkeavuuksien erottelutarkkuudesta monimutkaisten äänisarjojen oppimisen yhteydessä

Reduced object related negativity response indicates impaired auditory scene analysis in adults with autistic spectrum disorder

Auditory Scene Analysis provides a useful framework for understanding atypical auditory perception in autism. Specifically, a failure to segregate the incoming acoustic energy into distinct auditory objects might explain the aversive reaction autistic individuals have to certain auditory stimuli or environments. Previous research with non-autistic participants has demonstrated the presence of an Object Related Negativity (ORN) in the auditory event related potential that indexes pre-attentive processes associated with auditory scene analysis. Also evident is a later P400 component that is attention dependent and thought to be related to decision-making about auditory objects. We sought to determine whether there are differences between individuals with and without autism in the levels of processing indexed by these components. Electroencephalography (EEG) was used to measure brain responses from a group of 16 autistic adults, and 16 age- and verbal-IQ-matched typically-developing adults. Auditory responses were elicited using lateralized dichotic pitch stimuli in which inter-aural timing differences create the illusory perception of a pitch that is spatially separated from a carrier noise stimulus. As in previous studies, control participants produced an ORN in response to the pitch stimuli. However, this component was significantly reduced in the participants with autism. In contrast, processing differences were not observed between the groups at the attention-dependent level (P400). These findings suggest that autistic individuals have difficulty segregating auditory stimuli into distinct auditory objects, and that this difficulty arises at an early pre-attentive level of processing