Lea Leinonen

I. Functional properties of neurons in lateral part of associative area 7 in awake monkeys

SummaryThe lateral part of area 7, area 7b, of alert, behaving macaque monkeys was investigated using transdural microelectrode recording technique. Two hundred twenty-eight cells from five hemispheres of four monkeys were isolated and studied. The functional properties of 2% of the cells isolated remained unidentified. Functions of the identified cells were prominently related to the spatial control of arm movements.Of the cells 70% responded to somatosensory (40%) or visual (16%) or both somatosensory and visual (14%) stimulation. The receptive fields of these passively drivable cells were large, covering, e.g., the arm or leg or chest or even the skin of the whole body. Most of the visually drivable cells responded to stimuli in both halves of the visual field.Of the cells responding to sensory stimulation 80% were activated by stimuli moving in a certain direction. Of the directionally selective cells 25% received information through more than one sensory channel. The complex stimulus-response relationships of these “convergence” cells revealed the existence of an integrative system which analyzes the direction of a stimulus moving in one sensory system using an other sensory system as a reference.Of all the cells isolated 28% discharged only during active movements of the arms (25%) or eyes (3%). Firing of these neurons was related to contraction of a functionally uniform group of muscles and not individual muscles.Some previous investigations of the parietal association cortex, conducted mainly in area 7a, have shown that most cells are active only when the monkey himself moves his eyes or arms. In our study on area 7b most cells responded to passive stimulation. The discrepancy between the results indicates functional differentiation within area 7.

II. Functional properties of cells in anterolateral part of area 7 associative face area of awake monkeys

SummaryThe most anterior part of area 7 of awake, behaving macaque monkeys was investigated using single cell recording technique. Eighty-five cells from three hemispheres of two monkeys were isolated and studied. These cells showed more complex functional properties than the cells in the primary and secondary cortical fields. Of the cells 61% responded to somatosensory (26%) or visual (2%) or both somatosensory and visual (33%) stimulation; 39% of the cells were active only during the monkeys own movements.Most of the cells studied were active while the monkey was bringing an object to the mouth with its hand, when reaching for an object with lips, or while chewing. The neurons responded selectively to, e.g., palpation of the flexors of the arm, a visual stimulus approaching the face, passive movement of the monkeys hand towards the mouth, or they were active only when the monkey was reaching for an object with its lips or was mouthing it.The cellular activity in the anterolateral part of area 7 was prominently related to the stimulation or motor activity of the face (especially the mouth). In this respect, it differed from the more posterior part of area 7 adjacent to it. The results thus indicate that there is a separate and rather extensive mouth (or face) area in the parietal association cortex of the monkey.

Functional properties of neurons in the temporo-parietal association cortex of awake monkey

SummaryThe temporo-parietal association cortex around the caudal end of the Sylvian fissure was studied with the single cell recording technique in three awake behaving Macaca speciosa-monkeys. Of the 197 cells isolated, 5% were active only during the monkeys own movements, mostly during head rotation, and 95% were responsive to sensory stimulation: 54% to auditory stimuli, 24% to somatosensory stimuli, 13% to both of these and 4% to visual stimuli. Some cells, classified as responsive to somatosensory stimuli, were activated only by passive rotation of the head on the cervical axis; it is possible that they were driven by vestibular stimuli. Half of the cells were activated by stimuli on both sides of the monkey, and almost all the rest, only by stimuli on the side contralateral to the hemisphere recorded.Of the acoustically drivable cells, 95% responded to natural sounds, such as, rubbing hands together, rustle of clothes, clicks or jingles (sounds with noise spectrum and rapid intensity transitions). Most of these neurons were also examined with pure tones of 0.2–20 kHz: various inhibitory or excitatory responses were elicited in half of them, usually over a wide range of frequencies. The responses of most acoustically drivable cells (62%) depended on the location of the sound source with reference to the monkeys head so that the maximal response was elicited by sounds with a certain angle of incidence, usually on the contralateral side.The present results suggest that the area studied participates in the analysis of the temporal pattern of a sound, the location of the sound source and in spatial control of head movements.

Melatonin, cortisol and body temperature rhythms in Lennox-Gastaut patients with or without circadian rhythm sleep disorders.

The daily rhythms of melatonin, cortisol and body temperature were studied in 16 institutionalized subjects with the Lennox-Gastaut syndrome. The results of 9 subjects with normal daily rhythms of sleep and wakefulness (group 1) were compared with those of 7 subjects with disordered sleep (group 2). Salivary samples were collected and axillary temperature was measured every 2 h during two or three separate 26-h periods. The hormones were measured by radioimmunoassays. The rhythms were characterized with single cosinor analysis. Two subjects in group 1 and six subjects in group 2 had abnormalities in their rhythms of temperature, cortisol or melatonin. All three rhythms were disrupted in two subjects of group 2. These two subjects were the only ones with disrupted cortisol rhythm. The diversity of rhythm pathologies suggested partly separate regulatory mechanisms for each rhythm. The co-occurrence of circadian rhythm sleep disorders with the deteriorated melatonin rhythm raised the question as to whether the sleep disorders of these subjects, like those of subjects with healthy brains, could be relieved by the induction of normal melatonin rhythm.

Neurological impairments and sleep–wake behaviour among the mentally retarded

The objective of the present study was to evaluate the relationship between the sleep–wake behaviour and neurological impairments among mentally retarded people. The sleep–wake behaviour of 293 mentally retarded subjects living in a rehabilitation center was studied by a standardized observation protocol carried out by trained staff members. The protocol consisted of brief check‐ups of the subjects’ sleep–wake status at 20‐min intervals for five randomly chosen 24‐h periods during 4 months. From the raw data five sleep–wake behaviour variables were formed. The data concerning the subject characteristics (age, body mass index (BMI), gender, degree of mental retardation, presence of locomotor disability, that of epilepsy, blindness or deafness and the usage of psychotropic medications) were collected from the medical records. Two main findings emerged: (1) severe locomotor disablity, blindness and active epilepsy were found to be independent predictors of increased daytime sleep and increased number of wake–sleep transitions and (2) the subjects with a combination of two or all three of these impairments had a significantly more fragmented and abnormally distributed sleep than those with none or milder forms of these impairments. Age, BMI, degree of mental retardation and the studied medications played a minor role in the sleep disturbances of the study population. Finally, deafness was not found to be associated with any of the measured sleep–wake variables.

Self‐organized acoustic feature map in detection of fricative‐vowel coarticulation

The self-organizing map, a neural network algorithm of Kohonen, was used for the detection of coarticulatory variation of fricative [s] preceding vowels [a:], [i:], and [u:]. The results were compared with the psychoacoustic classification of the same samples to find out whether the map had extracted perceptually meaningful features of [s]. The map distinguished samples of [s] in front of [u:] from those in front of [a:] or [i:] throughout the fricative duration. Samples of [s] preceding [a:] and [i:] were distinguished from each other only just before (about 40 ms) the vowel onset. The results agreed with the perceptual classifications. Most judgments (82%) of [s] in front of [u:] were correct, and this variant of [s] was recognized from the first and second halves of segmented fricatives equally well. Samples of [s] in front of [a:] and [i:] were distinguished from each other less accurately. When halves of segmented [s] were perceptually judged, the differentiation between the following [a] and [i] was possible only on the basis of the second half of the fricative. The results demonstrate that the self-organizing map is a useful tool for the extraction of intersubject regularities in speech spectra. The map also provides an easily understandable, on-line, visualization of speech that can be used as feedback in therapy and education.

Recognition of emotions in macaque vocalizations by children and adults

Adults and three groups of children, aged 5–6, 6–7 and 9–10 years (241 subjects) categorized 13 vocalizations of Macaca arctoides using drawings of five human emotions: aggression, fear, positive emotion, submission, and dominance. Most vocalizations were recognized by all groups. The proportion of ‘correct’ judgments increased from 42% to 59% with age. The two younger groups were similar in their performance; the children aged 9–10 years resembled the adults. The two youngest groups chose the categories ‘angry’ and ‘commanding’ more often than the older subjects. Intense fear vocalizations, identified correctly by most adults, were not so well recognized by the two youngest groups of children, who frequently regarded them as ‘aggressive’ or ‘commanding’.

Temporal Integration and Contrast Sensitivity in Foveal and Peripheral Vision

Spatial contrast sensitivity functions and temporal integration functions for gratings with dark surrounds were measured at various eccentricities in photopic vision. Contrast sensitivity decreased with increasing eccentricity at all exposure durations and spatial frequencies tested. The decrease was faster at high than at low spatial frequencies, but similar at different exposure durations. When cortically similar stimulus conditions were produced at different eccentricities by M-scaling, contrast sensitivity became independent of visual field location at all exposure durations tested. The results support the view that in photopic vision spatiotemporal information processing is qualitatively similar across the visual field, and that quantitative differences result from retinotopical differences in ganglion cell sampling. For gratings of constant retinal area temporal integration (improvement of contrast sensitivity with increasing exposure duration) was more extensive at high than at low retinal spatial frequencies but independent of cortical spatial frequency and eccentricity. For M-scaled gratings temporal integration was more extensive at high than at low cortical spatial frequencies but independent of retinal spatial frequency and eccentricity. The results suggest that the primary determinant of temporal integration is not spatial frequency but grating value that is calculated as AF2 square cycles (cycle2), where A is grating area and F spatial frequency.

Determinants of sexual behavior ofMacaca arctoides in a laboratory colony

Copulatory behavior of wild-born individually caged laboratory stumptail monkeys (Macaca arctoides) was investigated. The monkeys were paired daily for 20 min, and altogether 536 pairings were observed. The influence of the females menstrual cycle and social factors on male sexual activity was determined. The reactions of the other monkeys during a pairing, and masturbation behavior of the males were observed and described. It was found that when a male and female were paired daily their sexual activity remained on a rather constant and high level for months provided the pair could not see, touch, or smell each other between the pairings. In these conditions the most common copulatory behavior consisted of 3–4 ejaculations. When the couple lived continuously in adjacent cages, which allowed them visual, tactual, and olfactory communication between pairings, the male ejaculated, on the average, only once during five successive pairings. Thus separation and reunion was potent in triggering sexual activity. When the couple was visually separated between sessions the males sexual activity did not depend on the menstrual cycle of the female. The males initiated copulation and the females were always willing, except in later stages of pregnancy, to cooperate. All males masturbated to ejaculation and it was often triggered by copulation, masturbation, or any happening causing arousal in the colony. The females were never seen to masturbate outside of the heterosexual context.

Vocal Communication between Species: Man and Macaque.

Abstract Naive human listeners (75 subjects) classified 18 vocalizations of Macaca arctoides into one of seven semantic categories. The classifications were compared with the categorization based on the overall behavioural situations in which the vocalizations were emitted. Sixty per cent of all answers were correct. More than 80% of the subjects identified correctly the vocalizations of female satisfaction and male dominance. At the other extreme nobody identified the threat grunts of a female. The results suggest that monkey and man share vocalization patterns signalling fear, aggression, dominance and emotional neutrality.