Abstract

Background: So far there has been no empirically proven taxonomy of mental functions which summarizes brain functions from a neuropsychological perspective. The classification of mental functions by Pöppel (1993, 1997) explains the correlation of the elementary functions from a neuropsychological point of view, based on a psychology of time. He distinguishes four levels of cognition: the cognition of simultaneity, of succession, of the subjective present, and of duration. These levels of cognition are based on two different brain mechanisms of temporal organization: a high-frequency mechanism that provides discrete systemic conditions of 30ms, within which all information that is processed separately in the brain is synchronized, and a low-frequency mechanism that summarizes subsequent systemic conditions from 30ms up to a limit of 3 seconds. Together with the function that provides a certain level of activation, these two functions form the logistical functions of the classification of mental functions. They provide not only the basis of temporal cognition, but also of that which can be subjectively experienced, i.e., of our perceptions (representation or perceptual processing of stimuli), memories (stimulus processing or storage of information), emotions (evaluation of stimuli), and action, respectively reaction (response to stimuli). These four domains are the content-related functions of the classification of mental functions. Objective: The objective of this paper is to determine to what extent empirical data collected from a (neuro-) psychological test battery reflect the representation of the mental functions postulated in theory. The specific goal is the factor-analytical representation of the classification of mental functions according to Pöppel (1993, 1997) by means of the individual tests. Methods: Healthy subjects aged 50 to 65 years without age-associated impairment participated in the pharmacologically-sponsored clinical study. Based on the theory of mental functioning, 15 (neuro-) psychological tests were selected to assess the repertoire of content-related and logistical functions. Nine tests were selected to assess content-related functions and six to assess logistical functions. To further test the dimensionality of Pöppel’s classification, a factor analysis was conducted to indicate to what extent the measuring instruments cover the mental functions in Pöppel’s classification. Results: The content-related function stimulus representation is covered completely, the function action/reaction is covered by variables in two out of three tests. The dimension emotional evaluation of information is largely covered. Temporal reproduction units of <3000ms and 3000ms as essential components of the low-frequency-mechanism of the logistical function temporal organization is distributed in two factors. High-frequency temporal organization of 30ms could not be verified in the present study as well as the function activation/attention. Another factor combines variables of temporal organization and of content implementation. The total variance explained by six factors was 62.1%. Conclusions: The results of the factor-analytical scale replication generally confirm the six given dimensions of the classification. Four of the six mental functions could be represented satisfactorily through factor analysis. Additionally, new aspects of the attribution of the instruments to the theory of mental functions can be assessed. The differentiation becomes most evident within time frames of under and over 3 seconds. The temporal limit of 3 seconds is theoretically assumed to be the threshold between subjective present and the perception of duration. Temporal Organization of 30-40Hz could not be reproduced by factor analysis in the given tests. This time unit is thought to be the threshold between the experience of simultaneity and succession of stimuli. In addition, one dimension comes to the fore that combines the content-related and the logistical components of the brain. The test battery obviously cannot represent some functions in isolation from each other. There may be a dimension on a different level of processing that combines content-related and logistical functions. This event provides evidence for the theoretical assumption of a close connection of content-related and logistical functions. With this study, an important move has been made, to use the classification of mental function for clinical practice. Via selective diagnosis of a deficient function, specific intervention can be implemented. In particular, the logistical functions of the classification have been neglected in neuropsychological practice. An appropriate system of classification is a prerequisite for the scientific exploration of psychological phenomena.