Aneta Szymaszek

Individual differences in the perception of temporal order: The effect of age and cognition

Temporal-order judgements in the time range of some milliseconds were assessed by using two auditory tasks in 86 participants, aged from 20 to 69 years. Two stimulus presentation modes, binaural versus monaural, were compared. Elderly participants performed worse than the younger participants; however, different patterns of age-related declines were observed, depending on the presentation mode. In the monaural mode considerable deterioration was observed beyond 60 years of age, whereas in the binaural mode declines were found much earlier, from 40 years of age. Performance of the monaural task correlated with cognitive competences and provided important insight into neuronal timing mechanisms. In contrast, the binaural mode reflected a bias towards an integrated perception of sequential stimuli and was less related to cognitive resources. These findings provide evidence that age-related declines in human sequencing abilities involve, besides temporal mechanisms, also a mode-specific processing, presumably associated with different neuronal mechanisms.

Non-invasive alternating current stimulation induces recovery from stroke.

BACKGROUND Recovery of post-stroke deficits can be achieved by modulating neuroplasticity with non-invasive brain stimulation. To evaluate potential effects of repetitive transorbital alternating current stimulation (rtACS) on stroke recovery we carried out a randomized, drug-controlled clinical trial. METHODS Ninety-eight patients that had suffered ischemic stroke 21.4 months earlier were randomly assigned to either group D (n=30) receiving conventional drug therapy, group ACS (n=32) treated for 12 days with rtACS, or group D/ACS (n=36) receiving combined drug therapy/rtACS. Stroke severity level (SSL) was assessed by the NIH-NINDS stroke scale before and after treatment and at a 1-month follow-up to evaluate motor impairments (weakness, ataxia), sensory loss, visual field defects, and cortical deficits (aphasia, neglect). At each time point standard EEG recordings (10-20 system) were conducted. RESULTS Before therapy SSL was moderate (9.18 ± 0.78) without significant group difference (F =0.86, p=0.43). After 12 days of treatment, SSLs of groups ACS and D/ACS significantly improved by 22.5% and 25.1% over baseline, respectively, with no such change in the control group D (+3%). SSL improvements were mainly due to recovery of motor, sensory, and speech functions. After 1-month follow-up, an additional improvement of 9.7% and 9.4% was seen for the group ACS and D/ACS which led to a total change of +32.3% and +34.7% over baseline. EEG recordings revealed greater interhemispheric synchrony between both temporal lobes which were positively correlated with clinical outcome. CONCLUSIONS Non-invasive rtACS applied to post-stroke patients can modulate brain plasticity and induce recovery from neurological deficits long after the early post lesion recovery is over.

Divergent effects of age on performance in spatial associative learning and real idiothetic memory in humans

This study focuses on age-related differences concerning two kinds of spatial memory assessed by: (1) Paired Associates Learning (PAL) test from the CANTAB and (2) a test of Real Idiothetic Memory (RIM) using real-life settings. Despite a clear age-related drop in PAL that is reported in existing studies, age-related differences in idiothetic navigation still remain unclear. In our study we tested 80 healthy volunteers classified according to their age into two groups, i.e. young (aged from 20 to 29 years of life; n=40; 20M/20F) and elderly (from 64 to 77 years; n=40; 20M/20F) healthy volunteers. They were asked in the PAL test to remember the spatial location of visual patterns presented on a computer screen, and in the RIM test to walk on the arena in darkness in order to find a cue place and then to return to the start/exit point. A white noise was switched on at entering the cue place and switched off at leaving this place. Elderly subjects indicated poorer performance than their younger counterparts on the PAL test, as evidenced by all tested outcome measures. In contrast, for the RIM test no clear age effect was evidenced. In both tests no gender effect was observed. A dissociation in age-related changes for these two tests indicates that visuo-spatial associative learning and idiothetic navigation may have different cognitive control which is probably rooted in an interplay of different brain structures.

Neural Representation of Time and Timing Processes

This chapter reviews existing studies on neural representation of time and timing processes. New findings in clinical neuropsychology, functional magnetic resonance imaging, electrophysiology, and psychophysics are presented to explain how the temporal information is processed within our brains. The literature data are illustrated with results of our findings. We outline the taxonomy of time perception to provide a background for discussing existing experimental studies. Evidence has indicated that similar brain structures are involved in both subsecond and suprasecond timing, implicating that temporal processing in these two ranges is probably mediated by common neural networks.

Training-Induced Changes in Rapid Auditory Processing in Children With Specific Language Impairment: Electrophysiological Indicators

The brain’s ability to recognize acoustic changes occurring in rapid temporal succession is important for speech and successful language development. Children with specific language impairment (SLI) are characterized by deficient dynamics of temporal information processing (TIP) in the millisecond time range accompanied by disordered language development. Furthermore, previous studies have found that intervention based on amelioration of TIP resulted in improvement of both language and other cognitive functions. This study aimed to explain the changes associated with TIP training from the perspective of event-related potentials (ERPs). Thirty-six children aged 5–8 years (26 boys, 10 girls) diagnosed with SLI underwent two types of intense audio-visual computer intervention: experimental TIP training targeted at the millisecond time range (n = 18) or control non-TIP training (n = 18). Paired 50 ms tones of 1000 Hz and 1200 Hz were presented with inter-stimulus intervals (ISIs) of either 50 ms (Short ISI Condition) or 200 ms (Long ISI Condition). Auditory ERPs were measured in a passive oddball paradigm before and after each type of training. The mismatch negativity (MMN) paradigm was applied as an electrophysiological indicator of the brain’s ability to automatically detect violations of regularity in paired tones presented in rapid succession. Moreover, the P3a component was also analyzed. After 24 sessions of temporal training (in the experimental group) MMN amplitude enhancement was observed in both ISI conditions, reflecting increased efficiency in perceiving changes in rapid auditory sequences. In both experimental and control groups, P3a amplitude was enhanced in both ISIs. This may be due to the improvement of involuntary attention shifting to the auditory events involved in each training type. To conclude, temporal training, compared to non-temporal control training, improved the ability to detect changes in a rapid auditory stream in children with SLI.

Training in temporal information processing ameliorates phonetic identification

Many studies revealed a link between temporal information processing (TIP) in a millisecond range and speech perception. Previous studies indicated a dysfunction in TIP accompanied by deficient phonemic hearing in children with specific language impairment (SLI). In this study we concentrate in SLI on phonetic identification, using the voice-onset-time (VOT) phenomenon in which TIP is built-in. VOT is crucial for speech perception, as stop consonants (like /t/ vs. /d/) may be distinguished by an acoustic difference in time between the onsets of the consonant (stop release burst) and the following vibration of vocal folds (voicing). In healthy subjects two categories (voiced and unvoiced) are determined using VOT task. The present study aimed at verifying whether children with SLI indicate a similar pattern of phonetic identification as their healthy peers and whether the intervention based on TIP results in improved performance on the VOT task. Children aged from 5 to 8 years (n = 47) were assigned into two groups: normal children without any language disability (NC, n = 20), and children with SLI (n = 27). In the latter group participants were randomly classified into two treatment subgroups, i.e., experimental temporal training (EG, n = 14) and control non-temporal training (CG, n = 13). The analyzed indicators of phonetic identification were: (1) the boundary location (α) determined as the VOT value corresponding to 50% voicing/unvoicing distinctions; (2) ranges of voiced/unvoiced categories; (3) the slope of identification curve (β) reflecting the identification correctness; (4) percent of voiced distinctions within the applied VOT spectrum. The results indicated similar α values and similar ranges of voiced/unvoiced categories between SLI and NC. However, β in SLI was significantly higher than that in NC. After the intervention, the significant improvement of β was observed only in EG. They achieved the level of performance comparable to that observed in NC. The training-related improvement in CG was non-significant. Furthermore, only in EG the β values in post-test correlated with measures of TIP as well as with phonemic hearing obtained in our previous studies. These findings provide another evidence that TIP is omnipresent in language communication and reflected not only in phonemic hearing but also in phonetic identification.