Language acquisition and language ability

12.1 Sensory modules for language learning

Speech can be considered from a physical point of view. It ultimately represents a frequency mixture of sound waves, just like many other sounds.

Nevertheless, frequency investigations showed that peculiarities in the sound frequencies occurred in human speech.

Spoken language is divided into phonemes. They are the smallest meaning-bearing sounds of a language.

The analysis of the sound frequencies of phonemes showed that resonance phenomena occur in the speech apparatus of humans, in which characteristic resonance frequencies arise. These are mainly characterised by their overtones. These overtones are sorted according to their frequency and clearly characterise the phonemes of speech by their frequency. F1 is the first overtone, F2 the second. Other overtones occur, which are then designated F3, F4, etc.. They are no longer so important for understanding speech. These overtones are called formants.

According to the German Wikipedia (as of May 2021), the phonemes of the German language are marked by the following formants.

German vowel	IPA	Formant F1	Formant F2
U	u	320 Hz	800 Hz
O	o	500 Hz	1000 Hz
å	É�	700 Hz	1150 Hz
A	a	1000 Hz	1400 Hz
ö	ø	500 Hz	1500 Hz
ü	y	320 Hz	1650 Hz
ä	É�	700 Hz	1800 Hz
E	e	500 Hz	2300 Hz
I	i	320 Hz	3200 Hz

These are average values, as the general pitch varies somewhat from person to person.

To understand speech, the human brain must first analyse the formants during speech. Here, frequency detection is particularly important.

The human hearing system is well prepared for this task.

Sound waves reach the outer ear, which bundles them and directs them to the eardrum of the middle ear. The auditory ossicles (malleus, incus, stapes) transmit the vibrations of the eardrum, they are transferred via the oval window to the fluid of the cochlea. A travelling wave is thus created on the basilar membrane, which enables a transformation of the frequency into a site of maximum excitation.

Hair cells are activated at the maxima of the travelling wave and emit action potentials. The unwinding of the basilar membrane into the plane reveals that there is a clear connection between the location and the frequency.

Therefore, this auditory organ can very well recognise any formants. Now the brain must not only recognise these, but also store them and thus learn and recognise the phonemes of the language.

Storage takes place in the pontocerebellum.

The frequency signals from the sensory centre reach the pontocerebellum via the bridge nuclei and terminate at the granule cells, while the mean neuron of this nucleus strongly excites a free Purkinje cell (or Purkinje group). Through LTP and LTD, the current formants are burnt into the Purkinje cell. In this way, they can be recognised later, and the associated cerebellar neuron then reports the recognition to the cortex.

Further formants, different from these, are also learned by imprinting the following free Purkinje cells as soon as they reach the auditory system.

However, language is not the isolated occurrence of phonemes, but a chronologically well-ordered sequence of phonemes. Therefore, the brain must have the ability to link a recognised phoneme with a subsequent phoneme. In this way, it practically learns double phonemes, later triple phonemes, etc.

This is where the limbic system helps with its hippocampal rotation loop. Each recognised phoneme causes a cerebellum output that not only pulls into the cortex, but is sent from the cerebellum into the limbic rotation memory. There, the action potential constantly rotates in a circle. But it equally sends its action potentials to the speech centre at each loop pass and reports: I was the last phoneme recognised.

If a second phoneme is now recognised, the speech centre receives two inputs: The one just recognised causes the cerebellum to report the recognition to the speech centre. But likewise, the limbic system reports the presence of the cached phoneme. So there are two neurons active in the speech centre. They send their action potentials to the cerebellum via bridge nuclei, while a mean neuron activates a free Purkinje cell there. The double phoneme is now stored by LTP and LTD. If it occurs again later, this Purkinje cell (or group) reports the recognition of a double phoneme to the speech centre. At the same time, the excitation is sent to a new, free neuron in the limbic loop, so that the signal rotation of the double phoneme begins there. The first official act of this new limbic rotation signal is to stop the rotation of the two single phonemes that compose itself in the rotation loops. Next, it tells the speech centre (more precisely, the auditory centre) that it is the last recognised double phoneme by sending an action potential there with each loop pass. In this way, another subsequent phoneme can be combined with it to form a triple phoneme.

Thus, the language system first learns short words, then longer ones, then perhaps whole sentences or phrases, and finally complete poems or even whole novels.

At the same time, of course, the brain has to learn and understand the meaning of the phoneme sequences it learns.

These processes, if they were to take place in this way, should lead very quickly to language acquisition. In reality, however, it looks different. For example, the output neuron of the dentate nucleus, which reports the recognition of a phoneme to the cortex, must first send its axon to the cortex. This can take days. Similarly, it must send an axon to the limbic system - sometimes with the interposition of other neurons. There, a new rotation loop must be created that did not exist before. This must then send an axon to the speech centre and make contact there.

The many signalling pathways must first be established during language acquisition. This is also due to the fact that humans are born with an immature brain. This can best be seen in the postnatal development of the cerebellum or in the example of neuron maturation in the visual thalamus.

Once the structures are in place, further language acquisition is not difficult, especially in youth.

Human brain theory

12 Language acquisition and language ability

12.1 Sensory modules for language learning