{'fraction_non_alphanumeric': 0.03659305993690852, 'fraction_numerical': 0.002523659305993691, 'mean_word_length': 5.1, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Allometry of brain metabolism

Allometry refers to biological scaling relationships (1). With regard to metabolic rate, the earliest allometric studies demonstrated a complex inverse relationship between body size and resting metabolic rate (2⇓–4). Subsequent studies have focused, without much success, on describing the cellular mechanisms of this relationship. The energy requirements of the cell can be crudely divided into two areas: differentiated external work, such as muscle contraction, neuron firing, transepithelial transport, and the basic cellular homeostasis processes, such as maintaining the cellular milieu, temperature, and so forth, which all cells have in common. In the literature-based analysis by Hyder et al. (5) in PNAS, metabolic and functional data from the rat and human brain were evaluated in a top-down analysis of two phenomenological coefficients (Ps and Pns) that correspond to these energy sinks. Ps has units of ATP used per neuron per spike and represents the energy efficiency of neuron signaling. PnsA and PnsN have units of ATP used per neuron per second in astrocytes and neurons, respectively, and represent the energy efficiency to maintain cellular homeostasis, (i.e., steady-state ion gradients, temperature, and so forth). The total ATPase activity (Etot) in ATP used per second per square centimeter was reduced to: Etot = Ps × (neuron firing rate) + ΣPns × (specific cell density). What Hyder et al. determined in this study is whether the coefficients Ps and ΣPns were constants as a function of functional state and size of the brain.