Biomedical subjects

P Paavilainen

Publications and source records attributed to P Paavilainen.

At least 19 recordsLinked to original sources

PubMed2001

Common neural mechanism for processing onset-to-onset intervals and silent gaps in sound sequences.

Stimulus onset asynchrony (SOA) and inter-stimulus interval (ISI) are important factors in the perceptual organization of sound sequences. The present study tested whether these two temporal parameters are independently processed in the auditory system. Independence was studied by testing the additivity of mismatch negativity (MMN). Four conditions differing in their temporal regularities were administered: (1) constant SOA and ISI, (2) constant SOA and variable ISI, (3) constant ISI and variable SOA, and (4) variable SOA and ISI. The MMN elicited by simultaneous deviance from the constant SOA and ISI (Condition 1) was compared with an additive model calculated from the MMNs elicited in the other conditions. The amplitude of the MMN in Condition 1 was significantly larger than that of the modeled MMN, suggesting that SOA and ISI are processed by interactive or common neural mechanisms.

Acoustic Stimulation↗

PubMed2001

The additivity of the auditory feature analysis in the human brain as indexed by the mismatch negativity: 1+1 approximately 2 but 1+1+1<3.

The automatic auditory feature analysis in the human brain was investigated using the mismatch-negativity (MMN) component of the event-related potential. MMNs were recorded in ignore and attend conditions to stimuli deviating from the repetitive standard stimuli simultaneously either in one, two or three features (frequency, intensity, stimulus-onset asynchrony). If the processing of each of these three features is independent of the others, the MMNs to the double and triple deviants should equal to the sum of the MMNs elicited by the corresponding single deviants. The double-deviant MMNs were found to be additive but the triple-deviant MMN was clearly underadditive. The results suggest complex interactions between brain processes involved in analyzing several simultaneous deviant features.

Adult↗

PubMed2001

"Primitive intelligence" in the auditory cortex.

The everyday auditory environment consists of multiple simultaneously active sources with overlapping temporal and spectral acoustic properties. Despite the seemingly chaotic composite signal impinging on our ears, the resulting perception is of an orderly "auditory scene" that is organized according to sources and auditory events, allowing us to select messages easily, recognize familiar sound patterns, and distinguish deviant or novel ones. Recent data suggest that these perceptual achievements are mainly based on processes of a cognitive nature ("sensory intelligence") in the auditory cortex. Even higher cognitive processes than previously thought, such as those that organize the auditory input, extract the common invariant patterns shared by a number of acoustically varying sounds, or anticipate the auditory events of the immediate future, occur at the level of sensory cortex (even when attention is not directed towards the sensory input).

Auditory Cortex↗

PubMed2001

Preattentive processing of spectral, temporal, and structural characteristics of acoustic regularities: a mismatch negativity study.

In the present study we investigated the relationship between detecting violations of structural regularities of tone sequences and detecting deviations from temporal regularities or repetitive spectral auditory stimulus features. Twelve subjects were presented with randomized sequences of two tones (differing both in frequency and intensity) delivered alternately to the left and right ears at a constant stimulus onset asynchrony (SOA). In separate blocks, occasional deviant stimuli broke one, two, or three of the following regularities: spatial alternation, the constancy of SOA, or the dominant frequency-intensity conjunctions. Unlike the mismatch negativity (MMN) elicited by alternation-plus-SOA deviants, the MMN elicited by alternation-plus-conjunction deviants was approximately equal to the sum of the two corresponding single-deviant MMNs. These results suggest that the preattentive change-detection system processes infrequent violations of the structural regularities of sound sequences together with changes in temporal regularities, but separately from changes in repetitive spectral sound features. The MMN elicited by the triple-deviant stimuli corroborated these conclusions.

Adult↗

PubMed2001

Preattentive extraction of abstract feature conjunctions from auditory stimulation as reflected by the mismatch negativity (MMN).

Brain mechanisms extracting invariant information from varying auditory inputs were studied using the mismatch-negativity (MMN) brain response. We wished to determine whether the preattentive sound-analysis mechanisms, reflected by MMN, are capable of extracting invariant relationships based on abstract conjunctions between two sound features. The standard stimuli varied over a large range in frequency and intensity dimensions following the rule that the higher the frequency, the louder the intensity. The occasional deviant stimuli violated this frequency-intensity relationship and elicited an MMN. The results demonstrate that preattentive processing of auditory stimuli extends to unexpectedly complex relationships between the stimulus features.

Acoustic Stimulation↗

PubMed2000

Mismatch negativity and behavioural discrimination in humans as a function of the magnitude of change in sound duration.

This study investigated how duration changes are processed in the human brain as indexed by the mismatch negativity (MMN), a component of the auditory event-related potential (ERP) reflecting sensory memory. Subjects were presented with sequences of repetitive 100-ms white noise bursts interspersed by occasional duration deviants which were 1, 10, or 50 ms (decrements) or 110, 150, or 200 ms (increments) in duration. In a separate task, subjects were asked to detect deviants within the sequence via a button-press. MMN was elicited by both stimulus decrements and increments and increased in amplitude as a function of the amount of deviation from the standard duration except for the shortest, 1-ms deviant. Behavioural detection paralleled the MMN responses, suggesting a link between the processes underlying MMN and behavioural measures.

Acoustic Stimulation↗

PubMed1999

Independent processing of changes in auditory single features and feature conjunctions in humans as indexed by the mismatch negativity.

The mismatch negativity (MMN), an event-related potential component of the EEG, is elicited by violations of auditory regularities In the present study, the stimulus blocks contained two types of standard tones, differing from each other in frequency and intensity. MMNs were recorded to three different types of deviant stimuli: (a) feature deviants, differing from standards in their perceived locus of origin; (b) conjunction deviants, having the frequency of one of the standards and the intensity of the other; (c) double deviants, differing from standards in both (a) and (b). The MMN to double deviants was similar to the sum of the MMNs to feature and conjunction deviants. This result indicates that changes in simple stimulus features and conjunction of features are processed independently by the automatic sound change detection system indexed by MMN.

Adult↗

PubMed1999

Neuronal populations in the human brain extracting invariant relationships from acoustic variance.

The ability to extract invariant relationships from physically varying stimulation is critical for example to categorical perception of complex auditory information such as speech and music. Human subjects were presented with tone pairs randomly varying over a wide frequency range, there being no physically constant tone pair at all. Instead, the invariant feature was either the direction of the tone pairs (ascending: the second tone was higher in frequency than the first tone) or the frequency ratio (musical interval) of the two tones. The subjects ignored the tone pairs, and instead attended a silent video. Occasional deviant pairs (either descending in direction or having a different frequency ratio) elicited the mismatch negativity (MMN) of the event-related potential, demonstrating the existence of neuronal populations which automatically (independently of attention) extract invariant relationships from acoustical variance.

Acoustic Stimulation↗

PubMed1998

Temporal constraints of auditory event synthesis: evidence from ERPs.

The temporal constraints of auditory event synthesis were investigated using event-related potentials. Standard stimuli consisted of an initial constant-frequency segment followed by a frequency glide. Occasionally, stimuli deviating from this standard both in intensity and within the direction of the glide were presented in the otherwise repetitive sound sequence. Previous results suggested that such 'double' deviants elicit only a single mismatch negativity (MMN) if the two temporally separate deviant elements were integrated within a common unit. Two successive MMNs were elicited by double deviants when the initial constant-frequency segment of the sound was 250 ms long, but only one when this segment was 150 ms in duration. The results support the hypothesis that the auditory input is processed in approximately 200 ms long temporal integration windows.

Acoustic Stimulation↗

PubMed1998

Binaural information can converge in abstract memory traces.

Neural representations for abstract features of auditory stimuli were studied by presenting reading subjects with stimulus blocks composed of pairs of two closely spaced tones. There were frequent ascending standard pairs (i.e., the second tone was higher in frequency than the first tone) and occasional descending deviant pairs. Both types of pairs varied randomly over a wide frequency range. In separate blocks, the tones forming a pair were presented either to the same ear or to opposite ears. The deviant pairs elicited the mismatch negativity (MMN) in all conditions, which indicates that the brain can automatically extract and represent an abstract invariant feature (rise or fall) of stimulation above the point of binaural convergence and detect violations against it. Poor behavioral performance in an active discrimination task suggested that conscious discrimination processes can only partially use the outcome of the preattentive discrimination processes reflected by the MMN.

Acoustic Stimulation↗

PubMed1994

Mismatch negativity to changes in a continuous tone with regularly varying frequencies.

By using the mismatch negativity (MMN) component of the event-related potential, it was demonstrated that changes within a repetitively presented tone pattern can be automatically (i.e., involuntarily and attention-independently) detected by the human brain. Patterns consisting of 5 tones, immediately succeeding one another and differing in frequency, were delivered to subjects reading a self-selected book. There was a frequent, "standard" (P = 0.90) and an infrequent, "deviant" (P = 0.10) pattern presented in random order. The deviant pattern elicited the MMN even when the auditory stimulation was continuous, that is, no empty between-pattern interval indicated the beginning of a tone pattern. It may be concluded that the MMN mechanism is not necessarily timed by an "external" reference but is able to use "internal" units extracted from the repetitive structure inherent in the incessant flow of acoustic signals. The MMN paradigm seems to provide a tool to illuminate the organization of acoustic signals into auditory units.

Acoustic Stimulation↗

PubMed1994

Temporal integration of auditory information in sensory memory as reflected by the mismatch negativity.

Event-related potentials (ERPs) to different types of infrequent change in a tone pair composed of two closely spaced tones of different frequencies were recorded. The mismatch negativity (MMN), a change-specific component of the ERP, was elicited by reversing the order of the two tones, by repeating the first tone, by replacing the first tone with the second tone, or by omitting the second tone. The omission of the second tone, however, elicited the MMN only when the interval between the two tones was very short (offset to onset 40 or 140 ms) but did not when this interval was somewhat longer (240 or 340 ms). The pattern of the present results suggests that sensory-memory traces, as reflected by the MMN, integrate information about two closely spaced stimuli into a unitary sensory event.

Adult↗

PubMed1994

[Mismatch negativity (MMN) to very short interval between regular tones].

The Mismatch Negativity (MMN) component of the auditory event-related potential (AERP) is elicited by infrequent, physically "deviant" stimuli in a sequence of frequent homogeneous stimuli ("standard"), for instance, by a change in frequency, intensity or duration etc. When the inter-stimulus interval (ISI) of tone pips was occasionally shortened either to 300, 150, 75, 60 and 52 ms from regular ISI 600 ms, which resulted in the elicitation of MMN. The amplitude of MMN elicited by occasional shorter ISI was not reduced as a function of ISI shortening. This indicates that the MMN is not just due to activation of new afferent elements by deviant stimulus. Thus, by no means the elicitation of the MMN can be explained on the basis of the refractoriness.

Acoustic Stimulation↗

PubMed1993

Event-related potentials reveal a memory trace for temporal features.

Auditory event-related potentials (ERPs) were recorded from reading subjects while they were presented with 50 ms tone pips intervened by regular silent intervals of 550 ms. This interval was occasionally shortened either to 250, 100, 25, 10, or 2 ms, which resulted in the elicitation of the mismatch-negativity (MMN), a change-specific ERP component not elicited by tones appearing after the regular, longer intervals. This indicates that the MMN is not just due to new afferent elements activated by deviant but not standard stimuli. In addition, the present results suggest that the temporal parameters of acoustic stimulation are also encoded in memory traces which therefore are representations of auditory events rather than only of static stimulus aspects.

Adult↗

PubMed1993

Auditory processing in visual brain areas of the early blind: evidence from event-related potentials.

Auditory event-related potentials (ERPs) were recorded in early blind subjects and sighted controls when they attended to stimuli delivered to a designated ear under dichotic conditions. The scalp distribution of the processing negativity (PN), the endogenous negativity elicited by attended stimuli, was in the blind posterior to that in the sighted. This suggests that posterior brain areas normally involved in vision participate in auditory selective attention in the early blind. Furthermore, occasional higher-frequency tones in the to-be-ignored ear elicited a negativity (presumably the mismatch negativity; MMN) that had a posterior scalp distribution in the blind as compared to controls. This suggests that the posterior brain areas of the blind also participate in processing of auditory stimulus changes occurring outside the focus of attention.

Acoustic Stimulation↗

PubMed1993

Stimulus duration and the sensory memory trace: an event-related potential study.

The mismatch negativity (MMN) of the auditory event-related potential is elicited when a stimulus deviates from that represented by the neural memory trace developed by preceding stimuli. The effect of stimulus duration on this trace was studied by presenting sequences of 1000 Hz, 80 dB stimuli to subjects engaged in silent reading. Stimuli were, in different blocks, either of 4, 10, 30, 100 or 300 ms in duration. 5% of the stimuli were deviants which were either higher in frequency (1050 Hz) or lower in intensity (70 dB) than the standards. The "silent" period between two successive stimuli was constant at 300 ms. The minimum stimulus duration with which a distinct MMN was elicited by frequency deviants was 30 ms, but the MMN amplitude was not increased when stimulus duration was further prolonged. In contrast, the intensity MMN was elicited even when stimulus duration of 10 ms and its amplitude increased as a function of stimulus duration. Reaction times and hit percentages in response to these deviant stimuli in a separate discrimination task displayed analogous patterns of results.

Adult↗

PubMed1993

Mismatch negativity to slight pitch changes outside strong attentional focus.

The mismatch negativity (MMN) component of the auditory event-related potential (ERP) is elicited by infrequent, physically deviant stimuli in a sequence of frequent homogeneous stimuli ("standards"). It has been suggested that the MMN is generated by an automatic (attention-independent) neural mismatch process between the sensory input and a memory trace encoding the physical features of the standard stimulus. The MMN independence of attention was addressed in the present study. Standard stimuli and two types of deviant stimuli, differing from standards in frequency either "widely" (5%) or "slightly" (3%) were dichotically presented in random order at a very rapid rate. The subject attended either to left- or right-ear stimuli, counting the number of "slight deviants" in that ear. A reading condition with the same stimuli was also included. Even in the present attend conditions with very strong attentional focus, the MMN was elicited by the slight deviants in the unattended input stream. Furthermore, its amplitude was similar to that of the MMN elicited by the equivalent deviant stimuli during reading. The results suggest that auditory frequency is fully analyzed even in the absence of attention.

Adult↗

PubMed1993

Development of a memory trace for a complex sound in the human brain.

The development of a memory trace for a complex, unfamiliar sound in the human brain was studied by repeatedly presenting reading subjects with this sound ('standard') which was occasionally replaced by a slightly different sound ('deviant'). Deviants did not elicit the mismatch negativity, an index of automatic change detection in auditory cortex, in the beginning but did later during the session. This result reflects a gradual 'sharpening' of sensory information encoded in the memory trace: the representation of the standard stimulus eventually became precise enough to enable the cortical change-detector mechanism to detect a slight different stimulus.

Acoustic Stimulation↗