Insular cortex activity and the evocation of laughter

The insular cortex is fundamentally involved in the processing of interoceptive information. It has been postulated that the integrative monitoring of the bodily responses to environmental stimuli is crucial for the recognition and experience of emotions. Because emotional arousal is known to be closely coupled to functions of the anterior insula, we suspected laughter to be associated primarily with neuronal activity in this region. An anatomically constrained re-analysis of our imaging data pertaining to ticklish laughter, to inhibited ticklish laughter, and to voluntary laughter revealed regional differences in the levels of neuronal activity in the posterior and mid-/anterior portions of the insula. Ticklish laughter was associated specifically with right ventral anterior insular activity, which was not detected under the other two conditions. Hence, apparently, only laughter that is evoked as an emotional response bears the signature of autonomic arousal in the insular cortex

Exploration of the Neural Correlates of Ticklish Laughter by Functional Magnetic Resonance Imaging

The burst of laughter that is evoked by tickling is a primitive form of vocalization. It evolves during an early phase of postnatal life and appears to be independent of higher cortical circuits. Clinicopathological observations have led to suspicions that the hypothalamus is directly involved in the production of laughter. In this functional magnetic resonance imaging investigation, healthy participants were 1) tickled on the sole of the right foot with permission to laugh, 2) tickled but asked to stifle laughter, and 3) requested to laugh voluntarily. Tickling that was accompanied by involuntary laughter activated regions in the lateral hypothalamus, parietal operculum, amygdala, and right cerebellum to a consistently greater degree than did the 2 other conditions. Activation of the periaqueductal gray matter was observed during voluntary and involuntary laughter but not when laughter was inhibited. The present findings indicate that hypothalamic activity plays a crucial role in evoking ticklish laughter in healthy individuals. The hypothalamus promotes innate behavioral reactions to stimuli and sends projections to the periaqueductal gray matter, which is itself an important integrative center for the control of vocalization. A comparison of our findings with published data relating to humorous laughter revealed the involvement of a common set of subcortical center

Laughter is in the air: Involvement of key nodes of the emotional motor system in the anticipation of tickling

In analogy to the appreciation of humor, that of tickling is based upon the re- interpretation of an anticipated emotional situation. Hence, the anticipation of tickling contributes to the final outburst of ticklish laughter. To localize the neuronal substrates of this process, fMRI was conducted on 31 healthy volunteers. The state of anticipation was simulated by generating an uncertainty respecting the onset of manual foot tickling. Anticipation was characterized by an augmented fMRI- signal in the anterior insula, the hypothalamus, the nucleus accumbens and the ventral tegmental area, as well as by an attenuated one in the internal globus pallidus. Furthermore, anticipatory activity in the anterior insula correlated positively with the degree of laughter that was produced during tickling. These findings are consistent with an encoding of the expected emotional consequences of tickling and suggest that early regulatory mechanisms influence, automatically, the laughter circuitry at the level of affective and sensory processing. Tickling activated not only those regions of the brain that were involved during anticipation, but also the posterior insula, the anterior cingulate cortex and the periaqueductal gray matter. Sequential or combined anticipatory and tickling-related neuronal activities may adjust emotional- and sensorimotor pathways in preparation for the impending laughter response

Effects of early second language acquisition on the cortical language network in multilinguals: evidence from fMRI

Auf dem Gebiet der Spracherwerbsforschung gilt es als erwiesen, dass frühe Spracherfahrung die Sprachentwicklung nachhaltig beeinflusst. Der frühe Erwerb einer oder zweier Sprachen müsste sich deshalb unterschiedlich auf die Ausbildung späterer Sprachkompetenzen auswirken. Einige psycholinguistische Untersuchungen konnten dies betätigen. Bis heute wurde jedoch der Einfluss früher Zweisprachigkeit auf die Ausbildung des kortikalen Sprachennetzwerkes wenig erforscht. Diesen Aspekt der Sprachentwicklung untersucht die vorliegende Arbeit mittels funktioneller Magnetresonanztomographie (fMRI). Dazu wurden zwei Gruppen von Mehrsprachigen gebildet: die erste von „frühen Mehrsprachigen“, die eine Zweitsprache (L2) im Kleinkindalter (bis drei Jahren); die zweite von „späten Mehrsprachigen“, die eine Zweitsprache (L2) als Heranwachsende oder später (ab neun Jahren) gelernt haben. Im Gegensatz zu früheren Arbeiten mit bildgebenden Verfahren beherrschten die in dieser Studie erfassten frühen und späten Mehrsprachigen eine weitere, als Heranwachsende oder später erworbene Drittsprache (L3). Die neuronale Hirnaktivität in den drei Sprachen (L1, L2 und L3) früher und später Mehrsprachiger wurde durch eine Sprachproduktionsaufgabe erfasst, somit auch für L3, wodurch der mögliche Einfluss früher Mehrsprachigkeit auf diese Drittsprache zum ersten Mal beurteilt werden konnte. Die sprachliche Aufgabe bestand darin, dass die Probanden in der jeweils getesteten Sprache über die Ereignisse des vergangenen Tages berichten mussten. Um den Einfluss nicht sprachspezifischer Einflüsse wie variable Aufmerksamkeit oder unterschiedlichen Bezug zum gerade Erlebten auf die gemessene Aktivierung zu verringern, wurde die Messung zweimal, und zwar an unterschiedlichen Tagen, durchgeführt. Die Durchschnittsaktivierungen von L1, L2 und L3 wurden für die Gruppen von frühen und späten Mehrsprachigen statistisch berechnet, wobei beide Messungen in die Auswertung einbezogen wurden. Der Vergleich der Hirnaktivität früh erworbener Sprachen zwischen beiden Gruppen früher und später Mehrsprachiger zeigte auffallende Unterschiede in der Nutzung des Sprachennetzwerkes. In der Tat gebrauchen die frühen Mehrsprachigen in ihren beiden früh gelernten Sprachen die Sprachregionen im Gehirn mehr als die späten Mehrsprachigen in ihrer Erstsprache. Höhere neuronale Aktivität wurde vor allem in Bereichen des linken Frontallappens, insbesondere im Broca Areal und dem daran angrenzenden präfrontalen Kortex beobachtet. Es ist bemerkenswert, dass sich früher Erwerb einer zweiten Sprache hier nicht nur auf die Funktion dieser Zweitsprache sondern auch auf diejenige der Erstsprache auswirkt. Die kortikale Region, welche offensichtlich durch die Auswirkung frühen Zweitsprachenerwerbs besonders in ihrer Funktion beeinflusst wurde – der präfrontale Kortex –, gilt als essentiell während der frühen prozeduralen Phase des Spracherwerbs. Dieser regionale Unterschied zwischen frühen und späten Mehrsprachigen weist darauf hin, dass in frühen Mehrsprachigen der Lösung von Interferenz zwischen den unterschiedlichen Sprachen eine grössere Bedeutung zukommt als in späten Mehrsprachigen. Tatsächlich weisen präfrontale Hirnregionen erhöhte neuronale Aktivität auf wenn zwischen konkurrierenden Bewegungsplänen entschieden werden muss; es ist wahrscheinlich, dass hier bei frühen Mehrsprachigen während des Spracherwerbvorgangs Interferenz zwischen den beiden damals gelernten Sprachen die Ausbildung des neuronalen Systems für den Sprechakt beeinflusst hat. Die vertiefte Auswertung der Studie gab einen weiteren Hinweis dafür, dass in frühen Mehrsprachigen kortikale Funktionen zur Interferenzlösung zwischen den beiden frühgelernten Sprachen abgestimmt sind. Diese Beobachtung ergibt sich aus dem Vergleich des sprachspezifischen Aktivierungsmusters beider Gruppen in perisylvischen Arealen der linken Hemisphäre, insbesondere im Broca-Areal und im supramarginalen Gyrus. Das neuronale Netzwerk, welches zwischen diesen Regionen ausgebildet ist, unterstützt unter anderem als „phonologischer loop“ sensorimotorische Integration phonologischer Information. In frühen Mehrsprachigen fällt die im Vergleich zu späten Mehrsprachigen überwiegend motorische Ausrichtung in der Aktivierung dieses Netzwerkes auf. Dies ist bekanntlich notwendig, wenn Interferenz zwischen sensorisch abgelegten phonologischen Sprachinformationen auftritt. Der Vergleich frühgelernter Sprachen zwischen frühen und späten Mehrsprachigen zeigte also, dass frühe Zweisprachigkeit die Funktion(en) des Sprachennetzwerkes dahingehend beeinflusst, dass eine Interferenz zwischen den Sprachen vermindert werden kann. Die Tatsache, dass die veränderte Hirnaktivität früher Mehrsprachiger im Erwachsenenalter nachweisbar ist, lässt darauf schliessen, dass sich der Einfluss früher Mehrsprachigkeit permanent auf die Funktion des sprachlichen Systems ausgewirkt hat. Der Vergleich der spätgelernten L3 zwischen den beiden Gruppen von Mehrsprachigen zeigte im Wesentlichen den gleichen Befund wie derjenige früh erworbener Sprachen: frühe Mehrsprachige greifen in ihrer Drittsprache vermehrt auf Hirnregionen zurück, welche Interferenzlösung unterstützen. Diese Studie konnte so zum ersten Mal einen Einfluss früher Mehrsprachigkeit auf die Funktion später erworbener Sprachen beschreiben. Ein Einfluss frühen Zweitsprachenerwerbs dahingehend, dass später gelernte Sprachen das bestehende Sprachnetzwerk besser nutzen können konnte, liess sich jedoch nicht feststellen. Tatsächlich wiesen in beiden Gruppen spät gelernte Sprachen ähnliche Unterschiede zu früh erworbenen Sprachen auf. Diese Studie zeigt, dass sich der Erwerb einer Zweitsprache zu einem frühen Zeitpunkt nicht allein auf die Funktion dieser einen Sprache auswirkt, sondern dass alle Sprachen, sogar erst später gelernte Sprachen beeinflusst werden. So konnte in dieser Arbeit die umfassende Bedeutung frühen Spracherwerbs für die Ausbildung des kortikalen Sprachnetzwerkes aufgezeigt werden.Research on language acquisition has shown that language development depends on language experience during early childhood. Early acquisition of one as opposed to two languages should therefore influence the development of language capabilities. Various psycholinguistic studies have provided support for this idea. The impact of early second language acquisition on the establishment of the cortical network, however, remains elusive. In the present study we used functional magnetic resonance imaging (fMRI) to investigate this aspect. Language related brain activity was assessed in two groups of multilinguals with different ages of second language acquisition: “early multilinguals” had acquired a second language (L2) in early childhood (before the age of three years); “late multilinguals” learned a second language (L2) in early adolescence or later (after the age of nine years). Of particular interest was the previously unexplained question of whether the brain representation of languages learned as adolescents or adults is influenced by early second language acquisition. With this perspective in mind, all early and late multilinguals included in the study had also learned a third language (L3) after the age of nine years, so that not only early, but also late learned languages could be compared between both groups. All multilinguals were tested in their three languages (L1, L2 and L3) by fMRI. The brain activity was measured during a language production task in which the subjects had to report the happenings of the previous day. To reduce influences not specifically related to language processes such as variable attention or valuation of the described experiences, the subjects were tested twice, on different days. The average brain activity during processing of L1, of L2 and of L3 has been statistically assessed for the groups of early and late multilinguals separately, including both tested runs. The comparison of the early acquired languages between both groups revealed striking differences in language related neuronal activity. Indeed, the analysis of the data shows that early multilinguals in both of their early acquired languages (L1 and L2) use cortical language regions more than late multilinguals in their L1. Particularly, increased neuronal activity was observed in regions of the left frontal lobe i.e. Broca’s area and the adjacent prefrontal cortex. It should be noted that the early acquisition of a second language (L2) determines not only its own cortical representation, but also that of the first acquired language (L1). The cortical region which is most influenced by the effect of early second language acquisition i.e. the prefrontal cortex, plays a crucial role during early procedural language acquisition. Here, higher activation could indicate the engagement of functions related to the resolution of cross-linguistic interference. Indeed, left prefrontal regions support processes necessary for a selection between competitive alternatives of a motor plan. In early multilinguals, specific cross-linguistic interference between the early acquired languages seemed to manifest itself during the preparation for the speech action. Further evaluation of the data provided more evidence for the involvement of cortical functions to resolve cross-linguistic interference between two early acquired languages. This is apparent from the comparison of the language-related activation pattern in left perisylvian regions between early and late multilinguals, particularly in Broca’s area and in the supramarginal gyrus. The neuronal network connecting these brain regions supports sensory-motor integration of phonological information, i.e. the function of the “phonological loop”. The evaluation led to the discovery of a pronounced motor load of the activated network in early multilinguals. It is known that such a functional adjustment is necessary to resolve interference of sensory related language information at the phonological level. Thus, the comparison of early acquired languages between early and late multilinguals could indicate, that early second language acquisition influences the function of the cortical language network to resolve various aspects of cross-linguistic interference. Since the changes in brain activity could be demonstrated in adults, the results of the present study indicate a persistent adaptation of brain language functions to the early presence of two languages. The comparison of the later-learned L3 between both groups showed principally the same result as the comparison of the early acquired languages: in early multilinguals, functions of language networks supporting resolution of language interference seem to be more established than in late multilinguals. This is the first study which has described an influence of early second language acquisition on the organisation of the cortical language network of subsequent late learned languages. An effect of early second language acquisition on the use of the language network by later-learned languages could however not be described. Indeed, later-learned languages of both groups showed similar differences to the early acquired languages. By demonstrating that exposure to a second language during early childhood not only manifests in the cortical language network of early but also of late acquired languages, this study extends the current view of the importance of early language acquisition for the establishment of the cortical language network

Exploration of the neural correlates of ticklish laughter by functional magnetic resonance imaging

The burst of laughter that is evoked by tickling is a primitive form of vocalization. It evolves during an early phase of postnatal life and appears to be independent of higher cortical circuits. Clinicopathological observations have led to suspicions that the hypothalamus is directly involved in the production of laughter. In this functional magnetic resonance imaging investigation, healthy participants were 1) tickled on the sole of the right foot with permission to laugh, 2) tickled but asked to stifle laughter, and 3) requested to laugh voluntarily. Tickling that was accompanied by involuntary laughter activated regions in the lateral hypothalamus, parietal operculum, amygdala, and right cerebellum to a consistently greater degree than did the 2 other conditions. Activation of the periaqueductal gray matter was observed during voluntary and involuntary laughter but not when laughter was inhibited. The present findings indicate that hypothalamic activity plays a crucial role in evoking ticklish laughter in healthy individuals. The hypothalamus promotes innate behavioral reactions to stimuli and sends projections to the periaqueductal gray matter, which is itself an important integrative center for the control of vocalization. A comparison of our findings with published data relating to humorous laughter revealed the involvement of a common set of subcortical centers

Olfactory impairment predicts brain atrophy in Parkinson's disease

Olfactory dysfunction is a frequent nonmotor symptom in idiopathic Parkinson's disease (PD) and may be considered as an early clinical feature of the disease preceding motor symptoms by years. According to recent neuropathological staging concepts, impaired olfaction is assumed to indicate an early pathological process and might be associated with structural changes in the brain. A morphometric analysis of magnetic resonance images [voxel-based morphometry (VBM)] was used to investigate gray matter atrophy related to psychophysically measured scores of olfactory function in early PD patients (n = 15, median Hoehn and Yahr stage 1.5), moderately advanced PD patients (n = 12, median Hoehn and Yahr stage 2.5), and age-matched healthy controls (n = 17). In PD patients, but not in controls, cortical atrophy in olfactory-related brain regions correlated specifically with olfactory dysfunction. Positive correlations between olfactory performance and gray matter volume were observed in the right piriform cortex in early PD patients and in the right amygdala in moderately advanced patients. The results provided first evidence that olfactory dysfunction in PD is related to atrophy in olfactory-eloquent regions of the limbic and paralimbic cortex. In addition, olfactory-correlated atrophy in these brain regions is consistent with the assumption that olfactory impairment as an early symptom of PD is likely to be associated with extranigral pathology

Early bilingualism influences early and subsequently later acquired languages in cortical regions representing control functions

Early acquisition of a second language influences the development of language abilities and cognitive functions. In the present study, we used functional Magnetic Resonance Imaging (fMRI) to investigate the impact of early bilingualism on the organization of the cortical language network during sentence production. Two groups of adult multilinguals, proficient in three languages, were tested on a narrative task; early multilinguals acquired the second language before the age of three years, late multilinguals after the age of nine. All participants learned a third language after nine years of age. Comparison of the two groups revealed substantial differences in language-related brain activity for early as well as late acquired languages. Most importantly, early multilinguals preferentially activated a fronto-striatal network in the left hemisphere, whereas the left posterior superior temporal gyrus (pSTG) was activated to a lesser degree than in late multilinguals. The same brain regions were highlighted in previous studies when a non-target language had to be controlled. Hence the engagement of language control in adult early multilinguals appears to be influenced by the specific learning and acquisition conditions during early childhood. Remarkably, our results reveal that the functional control of early and subsequently later acquired languages is similarly affected, suggesting that language experience has a pervasive influence into adulthood. As such, our findings extend the current understanding of control functions in multilinguals