## 1 Introduction
It is therefore pertinent to inquire in what way the human brain processes digits (simple numerals) different from number words (which could be considered as misused letters for the purpose of reflecting quantities). It appears that the well-known language areas primarily evolved to construct neural circuits that store and represent concepts of objects and other contents (see above). The concept of a quantity is qualitatively distinct from the concept of a tree (for example). Therefore, it seems evident that neural circuits designed to store concepts of objects may not be optimally suited for processing concepts of quantities. Just to clarify, it seems important to define relevant terminology. The term 'number' is here defined as a mental concept, or idea, about a distinct quantity. In contrast, a 'numeral' represents a way to symbolise a number, or quantity, for communication purposes. In other words, a numeral is a symbolic representation of a number, analogous to a string of letters representing semantic content (e.g., the word 'tree'). However, it is evident that there are two distinct methods of expressing a number in written form (as opposed to spoken language). As already mentioned above, one such method employs the use of number words (e.g., 'twelve'), while the other utilises digits (e.g., '12'). As previously stated, it could be argued that number words are, in fact, an abused language symbol meant to represent quantities (numbers). This raises the question of whether digits might be a more appropriate symbol for numbers than number words, particularly if the concept of a quantity is considered to be fundamentally different from the concept of an object. A series of letters constitutes a word that represents an idea of an object (e.g.,'spider'), whereas a series of digits forms a numeral that represents an idea of a number (i.e., a certain quantity of something). Number words may be less effective than digits in mediating distinct quantity processing in the human brain. As the question remains unresolved, the present study aimed to collect neurophysiological correlates with the highest possible temporal resolution to describe the differences in brain processes between number words and digits, while also comparing them with words and non-words. In particular, event-related potentials (ERPs) have been shown to be an invaluable tool for elucidating brief neurophysiological phenomena in the human brain [14; 15; 16; 17]. Consequently, we elected to employ ERPs in the present study. It is evident that our investigation into the human brain functions associated with number processing is not the first of its kind. However, it is noteworthy that the majority of previous studies in this field have placed a significant emphasis on developmental aspects, with the majority of these studies having been conducted with children [18; 19; 20; 21; 22]. The activity of the left parietal cortex has been observed in the context of the semantic representation of (Indic-) Arabic numerals [23]. The relationship between children's arithmetic ability and left intraparietal sulcus involvement has been previously described [24; 25; 26; 27]. The results of developmental studies have provided evidence for an increased specialisation of the left inferior parietal cortex region [28]. A tractographical investigation revealed a correlation between left fronto-parietal white matter and children's mathematical abilities [29]. Similarly, although less frequently observed, comparable findings have been documented in adult subjects [30]. Furthermore, studies employing individuals with dyscalculia [31] and alexia [32] have been utilised to enhance comprehension of number processing. Furthermore, the majority of studies employed functional magnetic resonance imaging (fMRI) as their primary methodology. Some studies have indicated that the bilateral intra-parietal sulcus (IPS) is a crucial region of the brain involved in the processing of numerals (number words).