**1. Introduction**

In the past two decades, an increasing number of studies have examined the human frontal lobe and PFC utilizing a wide variety of methodologies including stereology, MRI, minicolumn analysis, and DTI [1]. A number of recent studies have examined the relative size of gray and white matter in the frontal lobe or PFC, while others have examined the volume, neuron density, and columnar organization of functional subregions within the PFC. The frontal lobe includes several anatomical components and different functional areas, and, so it is thought that as a discrete unit can only tell us so much [2].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PFC plays most important roles in executive functions, which includes the organization of several sensory inputs, the maintenance of attention, planning, reasoning, language comprehension, the working memory, and the coordination of goal-directed behaviors [3–6]. Therefore, the functions of PFC are certainly a crucial aspect of what we think of as "human" in cognition [7].

**2. Structural development of the PFC**

In the third week of gestation, the first brain structure to arise is the neural tube, which is formed from progenitor cells in the neural plate [42]. In the sixth week, neuron production begins. Between gestational weeks 13 and 20, neuronal count increases rapidly in the tel-

[44]. Through some receptors and ligands, the nerve cells move from the source sites in the ventricular and subventricular regions to the main sites in the brain. Two basic types of cell migration, radial and tangential, have been described, and the most characteristic pattern is radial migration. The peak time period with these events is between 12 and 16 weeks of

Cortical organizational events begin in 20 weeks of pregnancy and continues. The basic developmental pattern in the cortical organization includes: (1) neurogenesis and differentiation of neurons, (2) formation and organization of cortical neuron layers, (3) dendritic and axonal branching, (4) formation of synapses, (5) cell death and pruning of synapses, and (6) glial

Primary sulci (superior frontal, inferior frontal, and precentral) are the main regions of the PFC, and develop during gestational weeks 25–26 [42]. The dorsolateral and lateral PFC arise during gestational weeks 17–25 [47]. The dendrites in Layer III and V continue to mature, as spines develop, basal dendritic length increases, and interneurons differentiate in layer IV

Synaptogenesis begins around the 20th gestational week. The formation and organization of synapses in the PFC increases after birth, reaches a peak, and is followed by pruning and decline like other neurodevelopmental processes. Also, synaptogenesis occurs later in the

After the other developmental stages, the latest developmental event is myelination [45]. Myelination begins in the 29th gestational week with the brain stem, and the development of white matter also follows a caudal to rostral progression like gray matter It continues until adulthood [49]. **Figure 1** shows the main developmental stages of brain intrauterine

At birth, total brain weight is about 370 g [50]. In a meta-analysis, it is showed that in all PFC areas, neuronal number measurements increase at every age point postnatally (0–72 months). Assessing the cortex as a whole, neuronal number increases 60–70% between 24 and 72 months postnatally [51]. Neuron density is 55% higher in the frontal cortex of 2-year-olds than it is in

Total gray matter volume is also greatest at the earlier stages of infancy. During infancy and childhood, gray matter volume in the frontal lobe is positively correlated with total brain

neurons at 20 weeks in the cortical plate and marginal zone

Development Period of Prefrontal Cortex http://dx.doi.org/10.5772/intechopen.78697 5

**2.1. Development in gestational period**

encephalon [43], with 5.87⋅109

proliferation and differentiation [45].

between 26 and 34 weeks [48].

PFC than it does in other areas.

**2.2. Development in infancy**

development.

adults [52].

pregnancy [45, 46].

The development of the brain occurs through the interaction of several processes, some of these stages are completed before birth such as neurulation, cell proliferation, and migration, although others continue into adulthood [8]. It is showed that the PFC is one of the last regions of the brain to mature, based on most indicators of development [9], and that the neurons in these areas have more complex dendritic trees than primary somatosensory and primary motor cortex those that mature earlier [10, 11]. Brain development begins in utero in the third gestational week and continues into adolescence [12]. However, lateral regions of the PFC are the latest developing areas that involved in executive functions [9].

When discussing the role of the PFC, other brain regions with which it shares intensive interconnections, including the basal ganglia, thalamus, brainstem, hippocampus, amygdala, and other neocortical regions also play important role [13, 14]. Thus, its intrinsic connections with other areas provide access to emotional responses and other information [5]. The lateral PFC is implicated in language and executive functions, while the orbital and medial regions of the PFC are thought to be involved in the processing and in the regulation of emotional behavior [15]. The lateral orbital PFC, interconnected regions of the basal ganglia, and the supplementary motor area, these regions are called the frontostriatal system, and they work together with many of the cognitive capacities [16].

PFC includes the following Broadman Areas (BA): 8, 9, 10, 11, 12, 44, 45, 46, 47. "The dorsolateral frontal cortex (BA) 9/46 has been functioned in many cognitive process, including processing spatial information [17–19], monitoring and manipulation of working memory [20, 21], the implementation of strategies to facilitate memory [22], response selection [23], the organization of material before encoding [24], and the verification and evaluation of representations that have been retrieved from long-term memory [25, 26]. The mid-ventrolateral frontal cortex (BA 47) has implicated cognitive functions, including the selection, comparison, and judgment of stimuli held in short-term and long-term memory [21], processing nonspatial information [27], task switching [28], reversal learning [29], stimulus selection [30], the specification of retrieval cues [25], and the 'elaboration encoding' of information into episodic memory [31, 32]. BA 10, the most anterior aspect of the PFC, is a region of association cortex known to be involved in higher cognitive functions, such as planning future actions and decision-making [33]. BAs 44 and 45, include part of the inferior frontal and these regions' functions are language production, linguistic motor control, sequencing, planning, syntax, and phonological processing [34, 35].

Finally, the orbitofrontal cortex mostly (BA 47, 10, 11, 13) in the orbitofrontal cortex has been implicated in processes that involve the motivational or emotional value of incoming information, including the representation of primary (unlearned) reinforcers such as taste, smell, and touch [36, 37], the representation of learnt relationships between arbitrary neutral stimuli and rewards or punishments [38, 39], and the integration of this information to guide response selection, suppression, and decision making" [40, 41].
