There is ample experimental evidence describing changes of tonotopic organisation in the auditory cortex due to environmental factors. In order to uncover the underlying mechanisms, we designed a large-scale computational model of the auditory cortex. The model has up to 100 000 Izhikevich's spiking neurons of 17 different types, almost 21 million synapses, which are evolved according to Spike-Timing-Dependent Plasticity (STDP) and have an architecture akin to existing observations. Validation of the model revealed alternating synchronised/desynchronised states and different modes of oscillatory activity. We provide insight into these phenomena via analysing the activity of neuronal subtypes and testing different causal interventions into the simulation. Our model is able to produce experimental predictions on a cell type basis. To study the influence of environmental factors on the tonotopy, different types of auditory stimulations during the evolution of the network were modelled and compared. We found that strong white noise resulted in completely disrupted tonotopy, which is consistent with in vivo experimental observations. Stimulation with pure tones or spontaneous activity led to a similar degree of tonotopy as in the initial state of the network. Interestingly, weak white noise led to a substantial increase in tonotopy. As the STDP was the only mechanism of plasticity in our model, our results suggest that STDP is a sufficient condition for the emergence and disruption of tonotopy under various types of stimuli. The presented large-scale model of the auditory cortex and the core simulator, SUSNOIMAC, have been made publicly available.

• Klíčová slova
• Auditory cortex, Large-scale model, Oscillation, STDP, Spiking neuron, Tonotopy,
• MeSH
• akční potenciály fyziologie   MeSH
• akustická stimulace MeSH
• lidé MeSH
• modely neurologické * MeSH
• nervová síť fyziologie   MeSH
• neurony fyziologie   MeSH
• počítačová simulace * MeSH
• sluchové korové centrum cytologie   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

We investigated the representation of four typical guinea pig vocalizations in the auditory cortex (AI) in anesthetized guinea pigs with the aim to compare cortical data to the data already published for identical calls in subcortical structures - the inferior colliculus (IC) and medial geniculate body (MGB). Like the subcortical neurons also cortical neurons typically responded to many calls with a time-locked response to one or more temporal elements of the calls. The neuronal response patterns in the AI correlated well with the sound temporal envelope of chirp (an isolated short phrase), but correlated less well in the case of chutter and whistle (longer calls) or purr (a call with a fast repetition rate of phrases). Neuronal rate vs. characteristic frequency profiles provided only a coarse representation of the calls' frequency spectra. A comparison between the activity in the AI and those of subcortical structures showed a different transformation of the neuronal response patterns from the IC to the AI for individual calls: i) while the temporal representation of chirp remained unchanged, the representations of whistle and chutter were transformed at the thalamic level and the response to purr at the cortical level; ii) for the wideband calls (whistle, chirp) the rate representation of the call spectra was preserved in the AI and MGB at the level present in the IC, while in the case of low-frequency calls (chutter, purr), the representation was less precise in the AI and MGB than in the IC; iii) the difference in the response strength to natural and time-reversed whistle was found to be smaller in the AI than in the IC or MGB.

• MeSH
• akustická stimulace MeSH
• druhová specificita MeSH
• morčata MeSH
• neurony fyziologie   MeSH
• sluchové evokované potenciály MeSH
• sluchové korové centrum fyziologie   MeSH
• vokalizace zvířat fyziologie   MeSH
• zvířata MeSH
• Check Tag
• morčata MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The inferior colliculus (IC) plays a strategic role in the central auditory system in relaying and processing acoustical information, and therefore its age-related changes may significantly influence the quality of the auditory function. A very complex processing of acoustical stimuli occurs in the IC, as supported also by the fact that the rat IC contains more neurons than all other subcortical auditory structures combined. GABAergic neurons, which predominantly co-express parvalbumin (PV), are present in the central nucleus of the IC in large numbers and to a lesser extent in the dorsal and external/lateral cortices of the IC. On the other hand, calbindin (CB) and calretinin (CR) are prevalent in the dorsal and external cortices of the IC, with only a few positive neurons in the central nucleus. The relationship between CB and CR expression in the IC and any neurotransmitter system has not yet been well established, but the distribution and morphology of the immunoreactive neurons suggest that they are at least partially non-GABAergic cells. The expression of glutamate decarboxylase (GAD) (a key enzyme for GABA synthesis) and calcium binding proteins (CBPs) in the IC of rats undergoes pronounced changes with aging that involve mostly a decline in protein expression and a decline in the number of immunoreactive neurons. Similar age-related changes in GAD, CB, and CR expression are present in the IC of two rat strains with differently preserved inner ear function up to late senescence (Long-Evans and Fischer 344), which suggests that these changes do not depend exclusively on peripheral deafferentation but are, at least partially, of central origin. These changes may be associated with the age-related deterioration in the processing of the temporal parameters of acoustical stimuli, which is not correlated with hearing threshold shifts, and therefore may contribute to central presbycusis.

• Klíčová slova
• GABA, aging, calbindin, calretinin, inferior colliculus, parvalbumin, rat,
• Publikační typ
• časopisecké články MeSH

Individual nuclei of the auditory pathway contribute in a specific way to the processing of complex acoustical signals. We investigated the responses of single neurons to typical guinea pig vocalizations (purr, chutter, chirp and whistle) in the ventral part of the medial geniculate body (MGB) of anesthetized guinea pigs. The neuronal and population peristimulus time histograms (PSTHs) reflected the repetition frequency of individual phrases in the calls. The patterns of PSTHs correlated well with the sound temporal envelope in calls with short phrases (purr, chirp). The dominant onset character of the neuronal responses resulted in a lower correlation between the sound envelope and the PSTH pattern in the case of longer calls (chutter and whistle). A time-reversed version of whistle elicited on average a 13% weaker response than did the natural whistle. The rate-characteristic frequency (CF) profile provided only a coarse representation of the sound frequency spectrum without detailed information about the individual spectral peaks and their relative magnitudes. In comparison with the inferior colliculus (Suta et al. in J Neurophysiol 90:3794-3808, 2003), the processing of species-specific vocalizations in the MGB differs in: (1) a less precise representation of the temporal envelope in the case of longer calls, but not in the case of calls consisting of one or more short phrases; (2) a less precise rate-CF representation of the spectral envelope in the case of low-frequency calls, but not in the case of broad-band calls; (3) a smaller difference between the responses to natural and time-reversed whistle.

• MeSH
• akční potenciály fyziologie   MeSH
• akustická stimulace MeSH
• časové faktory MeSH
• druhová specificita MeSH
• metathalamus cytologie   fyziologie   MeSH
• morčata MeSH
• neurony fyziologie   MeSH
• reakční čas fyziologie   MeSH
• sluchová percepce fyziologie   MeSH
• spektrální analýza MeSH
• vokalizace zvířat fyziologie   MeSH
• vztah dávky záření a odpovědi MeSH
• zvířata MeSH
• Check Tag
• morčata MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH