Filter Results
6 results
An important aspect of cognitive control is the ability to overcome interference, by boosting the processing of task-relevant information while suppressing the irrelevant information. This ability is affected by the progressive cognitive decline observed in aging. The aims of this study were to shed light on the neural spectral dynamics involved in interference control and to investigate age-dependent differences in these dynamics. For these reasons two samples of participants of different ages (23 younger and 20 older adults, age range = [18 35] and [66 82], respectively) were recruited and administered a spatial Stroop task while recording electroencephalographic activity. Scalp- and source-based time-frequency analyses revealed a main role of theta and beta frequencies in interference control. Specifically, for the theta band, we found age-dependent differences both for early event-related spectral perturbation (ERSP) Stroop effects at the source level – which involved dorsomedial and dorsolateral prefrontal cortices – and for related brain-behaviour correlations. This ERSP Stroop effect in theta was greatly reduced in magnitude in the older group and, differently from what observed in younger participants, it was not correlated with behavioural performance. These results suggest an age-dependent impairment of the theta-related mechanism signalling the need of cognitive control, in line with existing findings. We also found age-related differences in ERSP and source spectral activity involving beta frequencies. Indeed, younger participants showed a specific ERSP Stroop effect in beta – with the main involvement of left prefrontal cortex – whereas the pattern of older participants was delayed in time and spread bilaterally over the scalp. This study shows clear age-related differences in the neural spectral correlates of cognitive control. These findings open new questions about the causal involvement of specific oscillations in different cognitive processes and may inspire future interventions against age-related cognitive decline.
Data Types:
  • Document
Age related changes in neural oscillations, such as a slowing of frequency and a decrease in power, have been well established in previous research. However, neural “noise” has also been shown to change with age. This noise is considered an aperiodic component of the neural signal and has been shown to affect periodic components of the signal (i.e. oscillations), making it physiologically meaningful. Further, the 1/f component of the aperiodic signal has been found to represent the decoupling of population spiking activity from oscillatory synchronization. This desynchronization leads to a flatter 1/f slope which could help explain a decrease in cognitive function with age. In this study, we investigate how the role of the 1/f component of the aperiodic signal changes with age.
Data Types:
  • Document
We encounter multisensory environmental oscillations that span a wide range of temporal frequencies. In both audition and touch, sensory cues comprising repeating events are perceived either as a continuous signal or as a stream of temporally discrete events (flutter), depending on the events’ repetition rate. At high repetition rates (>100Hz), auditory and tactile cues interact reciprocally in pitch processing: The frequency of a cue experienced in one modality systematically biases the perceived frequency of a cue experienced in the other modality. Here, we tested whether audition and touch also interact in the processing of low-frequency stimulation. Because some neural populations have been shown to represent both auditory and tactile flutter, we predicted reciprocal multisensory interactions in flutter perception. We also tested whether multisensory interactions occurred if the stimulation in one modality comprised click trains and the stimulation in the other modality comprised amplitude-modulated signals, given that these stimulus types may be supported by distinct neural representations. In a series of human psychophysical experiments, we found that auditory cues bias touch and tactile cues bias audition on a flutter discrimination task. Moreover, we observed similar interaction patterns regardless of stimulus type and whether the same stimulus types were experienced in the two modalities. Combined with earlier studies, our results suggest that the nervous system extracts and combines temporal rate information from multisensory environmental signals, regardless of stimulus type, in both the low- and high temporal frequency domains. This function likely reflects the importance of temporal frequency as a fundamental feature of our multisensory experience.
Data Types:
  • Document
Thermodynamic principles of ideal solid are proposed. Here an ideal solid has perfectly harmonic lattice vibrations. Verifications of the total solution for the Schr ̈odinger equation of a solid revealed a fatal defect in the Debye model. That is, lattice vibrations at higher frequencies than the highest frequency ω H allowed in the solid would emerge immediately above 0K. The principles proposed in this paper fix that fatal defect by introducing thermal expansion to perfectly harmonic vibrations which relaxes those quantum harmonic oscillations excited to a higher eigen energy state than ̄hω H , where ̄ h is the reduced Planck constant. Thermal expansion, thereby, represses higher frequency vibrations which would inevitably emerge in the Debye model. The pressure for expansion reaches the upper limit at the melting point, and then the solid melts. Hence, the principles account for why ice melts at 273.15(K) ≃ ̄ hω H /(K B ln 2) = θ D / ln 2, where K B is the Boltzmann constant, θ D is the Debye temperature by definition, and ω H is the highest lattice vibration frequency in ice calculated from the molecular mass, spacing, and the speeds of sound for longitudinal and transverse waves in ice.
Data Types:
  • Document
The concept of “subject”, although is present in the reflection of human sciences since the time of classical philosophy, continues to present itself as complex and highly ambiguous. In psychoanalytic theory the paradox is concretized by the high frequence of the reference to the subject (in the Freudian Works the word subject appears more than a thousand times) but Freud never specified what is meant by this term. Moreover, in contemporary psychoanalysis in particular, expressions such as subjectivation and subjectivity are frequently used, even if there is no univocal conception of what a subject is. This paper aims to highlight how the subject is a polyphonic concept and how its escape from a definition is characteristic of its dynamism and its perpetual oscillation between the extremes of its semantic field, from subjection to substance.
Data Types:
  • Document
Planar Motion Mechanism (PMM) equipment is a facility generally attached with Towing Tank to perform experimental studies with ship models to determine the manoeuvring characteristics of a ship. Ship model is oscillated at prescribed amplitude and frequency in different modes of operation while it is towed along the towing tank at predefined speed.The hydrodynamic forces and moments are recorded, analyzed and processed to get the hydrodynamic derivatives appearing in the manoeuvring equations of motion of a ship. This paper presents the details about the Horizontal Planar Motion Mechanism (HPMM) equipment which is designed, developed and installed in Towing Tank laboratory at IIT Madras.
Data Types:
  • Document